Shell in Aleppo detonates (3)
I believe the answer is:
pod
'shell' is the definition.
('pod' can be a synonym of 'shell')
'in aleppo detonates' is the wordplay.
'in' says the answer is hidden in the clue.
'POD' is hidden within 'aleppo detonates'.
(Other definitions for pod that I've seen before include "The Borrowers father; seed case" , "Marine school" , "A long seed-vessel" , "Seed holder" , "Small school of whales" .)