Burden of remuneration for cargo? (7)
I believe the answer is:
payload
'burden' is the definition.
(thesaurus)
'remuneration for cargo?' is the wordplay.
'remuneration' becomes 'pay' ('pay' can be a synonym of 'remuneration').
'for' means one lot of letters go next to another.
'cargo?' becomes 'load' ('load' can be a synonym of 'cargo').
'pay'+'load'='PAYLOAD'
'of' is the link.
(Other definitions for payload that I've seen before include "Passengers, cargo or bombs" , "Cargo, bombs, on e.g. plane" , "Missile's warhead" , "Revenue-earning cargo" .)