Boost contained in carton I collected (5)
I believe the answer is:
tonic
'boost' is the definition.
(thesaurus)
'contained in carton i collected' is the wordplay.
'contained in' says the answer is hidden in the clue.
'TONIC' can be found hidden inside 'carton i collected'.
(Other definitions for tonic that I've seen before include "that may be mixed with gin" , "__water; gin mixer" , "requirement for invigoration?" , "something nice and fresh" , "Key" .)