Set on being taken over (3)
I believe the answer is:
gel
'set' is the definition.
(both can mean to harden)
'on being taken over' is the wordplay.
'on' becomes 'leg' (cricket term, fielding positions).
'being taken over' shows that the letters should be reversed in order.
'leg' back-to-front is 'GEL'.
(Other definitions for gel that I've seen before include "Preparation used in setting hair" , "Work well together" , "Solidify" , "Become jelly-like" , "Mousse" .)