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' (synonyms).
'for' says to put letters next to each other.
'cargo?' becomes 'load' ('load' can be a synonym of 'cargo').
'pay'+'load'='PAYLOAD'
'of' acts as a 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" .)