Set cricket side up (3)
I believe the answer is:
gel
'set' is the definition.
(both can mean to harden)
'cricket side up' is the wordplay.
'cricket side' becomes 'leg' (I've seen this before).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'leg' backwards is 'GEL'.
(Other definitions for gel that I've seen before include "Thicken" , "Jelly-like substance for leg" , "Leg (anag.)" , "It may be applied to locks" , "shock application?" .)