Ant biting foot of crown prince? Hard cheese! (9)
I believe the answer is:
emmenthal
'hard cheese' is the definition.
(emmenthal is a type of cheese)
'ant biting foot of crown prince?' is the wordplay.
'ant' becomes 'emmet' (synonyms).
'biting' is an insertion indicator (some letters bite or swallow others).
'foot of crown' becomes 'n' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'prince?' becomes 'hal' (Shakespearean nickname of Henry V when a prince).
'emmet' placed around 'n' is 'emment'.
'emment'+'hal'='EMMENTHAL'
Can you help me to learn more?
(Other definitions for emmenthal that I've seen before include "Type of cheese" , "Swiss valley giving its name to a cheese" , "Swiss cheese with holes" , "Hard Swiss cheese" , "Something cheesy" .)