Set on getting a rise (3)
I believe the answer is:
gel
'set' is the definition.
(both can mean to harden)
'on getting a rise' is the wordplay.
'on' becomes 'leg' (cricket term).
'getting a rise' says the letters should be written in reverse (in a down clue, letters go up).
'leg' reversed gives 'GEL'.
(Other definitions for gel that I've seen before include "shock application?" , "It may be applied to locks" , "Posh female" , "Become jelly-like" , "Mousse" .)