Going to try to get girl back (5)
I believe the answer is:
gonna
'going to' is the definition.
('I'm gonna' means 'I'm going to')
'try to get girl back' is the wordplay.
'try' becomes 'go' (both can mean an attempt).
'to get' says to put letters next to each other.
'girl' becomes 'ann' (woman's name).
'back' is a reversal indicator.
'ann' written backwards gives 'nna'.
'go'+'nna'='GONNA'
(Other definitions for gonna that I've seen before include "Going to (informal)" , "- - Build A Mountain (song)" , "Informally, about to get" , "Shortly intending to" .)