Warrior captures heart of free cargo ship (9)
I believe the answer is:
freighter
'cargo ship' is the definition.
(freighter is a kind of cargo ship)
'warrior captures heart of free' is the wordplay.
'warrior' becomes 'fighter' (I've seen this in another clue).
'captures' is an insertion indicator.
'heart of' says to take the centre.
The middle letters of 'free' are 're'.
'fighter' placed around 're' is 'FREIGHTER'.
(Other definitions for freighter that I've seen before include "Cargo ship" , "A plane carrying large load" , "Cargo-ship" , "Cargo-carrying ship or plane" , "transport vessel" .)