Petty officer stole this empty wagon (9)
I believe the answer is:
boatswain
'petty officer' is the definition.
'stole this empty wagon' is the wordplay.
'stole' becomes 'boa' (I've seen this before).
'empty' suggests removing the centre.
'wagon' becomes 'wain' (I've seen this before).
'this' with its middle taken out is 'ts'.
'boa'+'ts'+'wain'='BOATSWAIN'
(Other definitions for boatswain that I've seen before include "4 [TEMPEST] character" , "Officer on board" , "Seaman" , "Crew member" , "Merchant ship's petty officer" .)