Before and during approach (2,7)
I believe the answer is:
in advance
'before' is the definition.
(synonyms)
'during approach' is the wordplay.
'during' becomes 'in' (e.g. during February means in February).
'approach' becomes 'advance' (synonyms).
'in'+'advance'='IN ADVANCE'
'and' acts as a link.
(Other definitions for in advance that I've seen before include "Ahead in place or time" , "Beforehand - can invade accordingly (2.7)" , "Before the event" , "early" .)