Jog memory: what you may have to do to gain admission (4,1,4)
I believe the answer is:
ring a bell
'jog memory' is the definition.
(if something rings a bell you remember it)
'you may have to do to gain admission' is the wordplay.
I cannot really understand how this works, but
an anagram of 'gain' is 'inga' which is within the answer.
This may be the basis of the clue (or it may be nonsense).
'what' is the link.
Can you help me to learn more?
(Other definitions for ring a bell that I've seen before include "Campanologist might" , "stir a distant memory?" , "jog one's memory" , "Revive a dim memory" , "faintly resonate" .)