Overeat last of the new Cheddar? (7)
I believe the answer is:
engorge
'overeat' is the definition.
(synonyms)
'last of the new cheddar?' is the wordplay.
'last of' indicates one should take the final letters.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'cheddar?' becomes 'gorge' (Cheddar Gorge is a gorge in Somerset).
The last letter of 'the' is 'e'.
'e'+'n'+'gorge'='ENGORGE'
(Other definitions for engorge that I've seen before include "Congest with blood - eat greedily" , "Cause to swell with fluid" , "Get stuffed" , "Eat immodestly" , "Guzzle" .)