Warplane circling about cargo ship (9)
I believe the answer is:
freighter
'cargo ship' is the definition.
(freighter is a kind of cargo ship)
'warplane circling about' is the wordplay.
'warplane' becomes 'fighter' (I've seen this before).
'circling' is an insertion indicator (circling can mean going around or containing).
'about' becomes 're' (regarding).
'fighter' enclosing 're' is 'FREIGHTER'.
(Other definitions for freighter that I've seen before include "Cargo-carrying ship or plane" , "transport vessel" , "Cargo-ship" , "Cargo ship" , "A plane carrying large load" .)