Witty colonel drinking mineral (7)
I believe the answer is:
comical
'witty' is the definition.
(I've seen this before)
'colonel drinking mineral' is the wordplay.
'colonel' becomes 'col'.
'drinking' is an insertion indicator.
'mineral' becomes 'mica' (mica is a kind of mineral).
'col' going around 'mica' is 'COMICAL'.
(Other definitions for comical that I've seen before include "Witty" , "Amusing or droll" , "Causing laughter" , "priceless" , "Rich" .)