Fish (salmon) short of some oxygen, caught by a fleet out of area (7)
I believe the answer is:
anchovy
'fish' is the definition.
(anchovy is a kind of fish)
I cannot understand how the remainder of the clue works.
(Other definitions for anchovy that I've seen before include "Small edible fish" , "Small salty fish" , "Small fish used in making sauce, paste etc" , "Little fish, usually tinned or salted" , "Salty little fish" .)