Left-hander who smashes nothing with that hand (5)
I believe the answer is:
nadal
'left-hander who smashes' is the definition.
Although both the answer and 'left-hander' are adjectives, they are not in the same form of the adjective.
'nothing with that hand' is the wordplay.
'nothing' becomes 'nada' (synonyms).
'with' means one lot of letters go next to another.
'that hand' becomes 'l' (abbreviation for left, as in the left-hand side).
'nada'+'l'='NADAL'
Can you help me to learn more?
(Other definitions for nadal that I've seen before include "tennis champion" , "court figure" , "Star with a 30 [RACKET]" , "Top tennis player" , "Rafael __, Spanish tennis player" .)