Fish regularly found in warm stormy seas (6)
I believe the answer is:
wrasse
'fish' is the definition.
(wrasse is a kind of fish)
'regularly found in warm stormy seas' is the wordplay.
'regularly found in' means one should take alternating letters.
'stormy' is an anagram indicator.
The alternating letters of 'warm' are 'wr'.
'seas' with letters rearranged gives 'asse'.
'wr'+'asse'='WRASSE'
(Other definitions for wrasse that I've seen before include "Swears about the tropical marine fish with strong teeth" , "Type of fish" , "catch in the deep" , "Bony fish" , "Swimmer" .)