Sort of word used by clever bloke (4)
I believe the answer is:
verb
'sort of word' is the definition.
'used by clever bloke' is the wordplay.
'used by' indicates the answer is hidden within the clue.
'VERB' can be found hidden inside 'clever bloke'.
(Other definitions for verb that I've seen before include "Word such as run, make, or do" , "Type of word indicating action" , "'In grammar, it denotes action (4)'" , "A word that conveys action" , "Predicate of a sentance (4)" .)