A transgender woman has told a magistrate she swung a punch at a Sydney police officer after being "continually pushed" during her arrest for breaching bail.

Senior Constable Craig Norman Williamson, 30, has pleaded not guilty to the common assault of Nicolas Bradford, who identifies as Anya, in a Surry Hills police station cell in October 2018.

It is not in dispute that Williamson pushed Bradford.

"There's an acknowledgement ... by the accused that he used force," magistrate John Favretto said at Downing Centre Local Court on Monday.

"The issue here is whether it was reasonable and necessary in the circumstances."

Under cross-examination by defence barrister Brent Haverfield, Ms Bradford said she wasn't resisting arrest but "trying to stop the pain which meant I had to pull away ... as (Williamson) was hurting me".

Ms Bradford said she'd earlier called the police station stating she'd be late to report, as per her bail conditions, because she was homeless and had been at a friend's house in Parramatta.

She said she'd requested an ambulance but it wasn't called for her, adding that she was handcuffed at some stage and also told she would be strip searched.

Ms Bradford gave evidence she repeatedly said, "I'm clearly complying, please stop hurting me", during her arrest and alleged Williamson continually pushed her from the front of reception to the cell.

She swung a punch and struck Williamson when the handcuffs had been removed.

The court heard she was 15 to 20 minutes late to report to police that day but had breached her bail reporting conditions earlier that week which prompted the arrest.

Leading Senior Constable Charles Cook said the incident occurred while he was having dinner at the station.

He testified he spoke to Williamson while waiting for an ambulance to treat his facial injury from the punch.

"Craig said 'He claimed he was trans (and) I said 'No you're not, don't start that s***'," the officer told the court.

Sen Const Cook said he felt arresting Bradford had been "a reasonable course of action to take" given the complainant's previous failures to report to police.

Constable Ryan Barlow gave evidence he'd escorted Bradford into the custody area with Williamson that night.

He told prosecutor Kimberley McKenzie he saw Williamson step forward and push Bradford with a palm in the chest.

Ms McKenzie asked: "How would you describe Bradford in terms of size compared to that of the accused?"

"Very thin build, about half the size of Senior Constable Williamson," Const Barlow replied.

Williamson was charged in February and is currently suspended from duty, NSW Police confirmed on Monday.

The hearing will resume on September 25.