Charge bundle to catch rhea (7)
I believe the answer is:
warhead
'charge' is the definition.
(I've seen this before)
'bundle to catch rhea' is the wordplay.
'bundle' becomes 'wad' (synonyms).
'to catch' is an insertion indicator.
'wad' going around 'rhea' is 'WARHEAD'.
(Other definitions for warhead that I've seen before include "Missile explosive unit" , "bit of a weapon" , "Charge" , "Explosive part of a weapon" , "Missile's explosive" .)