Perform in Clacton (3)
I believe the answer is:
act
'perform' is the definition.
(acting is a kind of performing)
'in clacton' is the wordplay.
'in' says the answer is hidden in the clue.
'ACT' can be found hidden inside 'clacton'.
(Other definitions for act that I've seen before include "Produce an effect" , "Ordinance" , "turn" , "Perform - part of a play" , "Assumed attitude" .)