Rum MEP worried about one insurance payment (7)
I believe the answer is:
premium
'insurance payment' is the definition.
(I've seen this before)
'rum mep worried about one' is the wordplay.
'worried' indicates anagramming the letters.
'about' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'rum'+'mep'='rummep'
'rummep' with letters rearranged gives 'premum'.
'premum' placed around 'i' is 'PREMIUM'.
(Other definitions for premium that I've seen before include "highest quality" , "Insurance charge" , "Amount payable for insurance etc" , "best quality" , "Additional cost" .)