Superb exterior to masculine perfection (4)
I believe the answer is:
acme
'perfection' is the definition.
(thesaurus)
'superb exterior to masculine' is the wordplay.
'superb' becomes 'ac' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'exterior' says to hollow out the word (remove centre letters).
'masculine' with its middle taken out is 'me'.
'ac'+'me'='ACME'
Can you help me to learn more?
(Other definitions for acme that I've seen before include "Height of achievement" , "Peak of perfection" , "Height of excellence" , "high peak" , "Highest level or degree attainable" .)