Husband in car say reversed to fill up (6)
I believe the answer is:
charge
'fill up' is the definition.
(charging is a kind of filling up)
'husband in car say reversed' is the wordplay.
'husband' becomes 'h'.
'in' means one lot of letters goes inside another.
'say' becomes 'eg' (both can mean 'for example').
'reversed' says the letters should be written backwards.
'eg' in reverse letter order is 'ge'.
'h' placed into 'car' is 'char'.
'char'+'ge'='CHARGE'
'to' acts as a link.
(Other definitions for charge that I've seen before include "Accumulation of electricity" , "How much" , "Accuse - rush - request payment" , "Formally accuse; rush" , "Set price or mount onslaught" .)