Stray appointment I have put back in (7)
I believe the answer is:
deviate
'stray' is the definition.
(I've seen this in another clue)
'appointment i have put back in' is the wordplay.
'appointment' becomes 'date' (synonyms).
'i have' becomes 'I've' (contraction of 'I have').
'put back' shows that the letters should be reversed in order.
'in' indicates putting letters inside.
'ive' back-to-front is 'evi'.
'date' placed around 'evi' is 'DEVIATE'.
(Other definitions for deviate that I've seen before include "Depart from an established course" , "Go off track" , "Turn aside from course of action" , "Diverge (from a course)" , "Go off course" .)