Quiet country has endless fish (7)
I believe the answer is:
piranha
'fish' is the definition.
(piranha is a kind of fish)
'quiet country has endless' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano').
'country' becomes 'iran' (Iran is an example).
'endless' means to remove the last letter.
'has' with its last letter taken off is 'ha'.
'p'+'iran'+'ha'='PIRANHA'
(Other definitions for piranha that I've seen before include "Fierce small fish of the Amazon" , "Efficient flesh remover" , "Small voracious carnivorous fish" , "Voracious river fish" , "Voracious eater" .)