Citron Call is one of Lime Bell's special moves. It requires her special gauge to be full in order to use it.
Citron Call was initially thought to be a healing move as it returned the target's HP back to full. However, after the second battle between Silver Crow, Cyan Pile and Dusk Taker, it was revealed that Citron Call was actually a move that turns back time - Undoing damage on the target and take away their Special Gauge.
After leveling up, Lime Bell upgraded her move that allowed it to go further back in time, which led to Silver Crow getting his wings back from Dusk Taker.