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' indicates the answer is hidden within 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" .)