Grill hunting expedition over decapitated animal (8)
I believe the answer is:
question
'grill' is the definition.
(I've seen this in another clue)
'hunting expedition over decapitated animal' is the wordplay.
'hunting expedition over' becomes 'quest' (I am not sure about this - if you are sure you should believe this answer much more).
'decapitated' means to remove the first letter.
'animal' becomes 'lion' (I've seen this before).
'lion' with its initial letter taken away is 'ion'.
'quest'+'ion'='QUESTION'
Can you help me to learn more?
(Other definitions for question that I've seen before include "Query" , "See 17" , "Challenge" , "What could initiate this" , "Enquiry; doubt" .)