A girl put back some of the cargo (5)
I believe the answer is:
grace
'a girl' is the definition.
(I've seen this before)
'back some of the cargo' is the wordplay.
'back' shows that the letters should be reversed in order.
'some of' says the answer is hidden in the clue.
'ecarg' can be found hidden inside 'the cargo'.
'ecarg' backwards is 'GRACE'.
'put' acts as a link.
(Other definitions for grace that I've seen before include "Elegance; blessing" , "Prayer of thanks before/after a meal" , "For example, Euphrosyne" , "Before dinner, one may have this" , "cricketing great" .)