Fed up with the fish but settles the bill (7)
I believe the answer is:
defrays
'settles the bill' is the definition.
I can't tell whether this defines the answer.
'fed up with the fish' is the wordplay.
'up' is a reversal indicator (in down clue: letters go upwards).
'with' says to put letters next to each other.
'the fish' becomes 'rays' (I've seen this before).
'fed' reversed gives 'def'.
'def'+'rays'='DEFRAYS'
'but' acts as a link.
Can you help me to learn more?
(Another definition for defrays that I've seen is " Bears the expenses of".)