Thin male bore (6)
I believe the answer is:
meagre
'thin' is the definition.
(I've seen this before)
'male bore' is the wordplay.
'male' becomes 'm' (common abbreviation).
'bore' becomes 'eagre' (both can mean a wave).
'm'+'eagre'='MEAGRE'
(Other definitions for meagre that I've seen before include "unsatisfactorily small in amount" , "Miserable" , "Scanty, skimpy" , "Thin -- inadequate" , "Scanty in amount - puts me in rage" .)