Head leaving specimen — more than enough (5)
I believe the answer is:
ample
'enough' is the definition.
(ample means enough or plenty)
'head leaving specimen' is the wordplay.
'head leaving' means to remove the first letter.
'specimen' becomes 'sample' (I've seen this before).
'sample' with its initial letter taken away is 'AMPLE'.
'aeur more than' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for ample that I've seen before include "Generous" , "No more, please!" , "Big" , "Plenteous" , "Sealed glass container for dose of medicine" .)