Imogen apt to convert an advantage (4,5)
I believe the answer is:
game point
'an advantage' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I can't see?
'imogen apt to convert' is the wordplay.
'to convert' indicates an anagram (I've seen 'converted' mean this).
'imogen'+'apt'='imogenapt'
'imogenapt' is an anagram of 'GAME POINT'.
Can you help me to learn more?
(Other definitions for game point that I've seen before include "advantage possibly" , "Decisive moment" .)