Call up the day before to secure approval (5)
I believe the answer is:
evoke
'call up' is the definition.
('evoke' can be a synonym of 'call up')
'the day before to secure approval' is the wordplay.
'the day before' becomes 'eve' (I've seen this before).
'to secure' is an insertion indicator.
'approval' becomes 'ok' (OK is an example).
'eve' going around 'ok' is 'EVOKE'.
(Other definitions for evoke that I've seen before include "Awaken memories in the mind" , "Raise" , "Kindle (memory)" , "Awake memories" , "Prompt" .)