Fish wars spread to London area (6)
I believe the answer is:
wrasse
'fish' is the definition.
(wrasse is a kind of fish)
'wars spread to london area' is the wordplay.
'spread' is an anagram indicator.
'to london area' becomes 'SE' (postcode for south east London).
'wars' anagrammed gives 'wras'.
'wras'+'se'='WRASSE'
(Other definitions for wrasse that I've seen before include "Bright marine fish" , "catch in the deep" , "Bony fish" , "Swears about the tropical marine fish with strong teeth" , "Fish - swears (anag)" .)