Animal found in salt water loch (4)
I believe the answer is:
seal
'animal' is the definition.
(I have seen 'Marine animal' mean 'seal' so perhaps 'animal' could also mean 'seal')
'salt water loch' is the wordplay.
'salt water' becomes 'sea' (I've seen this before).
'loch' becomes 'l'.
'sea'+'l'='SEAL'
'found in' is the link.
(Other definitions for seal that I've seen before include "See 7" , "Close - (performing?) animal" , "Sea beast - authenticating mark" , "Insignia for sale" , "Fasten securely; aquatic mammal" .)