Back in parliament celebrating return (5)
I believe the answer is:
elect
'return' is the definition.
(I've seen this before)
'back in parliament celebrating' is the wordplay.
'back' shows that the letters should be reversed in order.
'in' indicates the answer is hidden within the clue.
'tcele' can be found hidden inside 'parliament celebrating'.
'tcele' back-to-front is 'ELECT'.
(Other definitions for elect that I've seen before include "Choose; chosen" , "Vote to put into power" , "Put into power through the ballot box" , "Make" , "Choose by voting" .)