Large box of matches to strike (5)
I believe the answer is:
'large box' is the definition.
(I've seen this before)
'of matches to strike' is the wordplay.
'of' says the answer is hidden in the clue.
'CHEST' can be found hidden inside 'matches to strike'.
(Other definitions for chest that I've seen before include "Bra on it" , "Large box; thorax" , "ark" , "Strong box; thorax" , "Large box used for storage" .)