Not straightforward the day before about returning official document (7)
I believe the answer is:
evasive
'not straightforward' is the definition.
(I've seen this in another clue)
'day before about returning official document' is the wordplay.
'day before' becomes 'eve' (the eve of something is the night before).
'about' indicates putting letters inside.
'returning' is a reversal indicator.
'official document' becomes 'visa' (travel document).
'visa' in reverse letter order is 'asiv'.
'eve' enclosing 'asiv' is 'EVASIVE'.
'the' acts as a link.
(Other definitions for evasive that I've seen before include "make out-of-the-way sort of action" , "Shifty, not giving straight answers" , "Deliberately vague" , "Trying to avoid commitment" , "Tending to avoid commitment" .)