Gain access to (3,2)
I believe the answer is:
get at
'gain access to' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for get at that I've seen before include "Nobble; gain access to" , "Criticise (someone)" , "Reach - mean - attack verbally" , "Unfairly influence" , "Pick on - gain access to" .)