Clown to run backwards on jetty (7)
I believe the answer is:
pierrot
'clown' is the definition.
(I've seen this before)
'to run backwards on jetty' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'backwards' is a reversal indicator.
'on' means one lot of letters go next to another.
'jetty' becomes 'pier' (I've seen this before).
'to'+'r'='tor'
'tor' reversed gives 'rot'.
'rot' put after 'pier' is 'PIERROT'.
(Other definitions for pierrot that I've seen before include "French pantomime character with a white face" , "French panto clown with whitened face" , "French stage character with white face and costume" , "Clown from French panto - tripe or what" , "Period; incantation" .)