Clue: Search and rescue by operations leader into nasty gasses across large part of the North Atlantic (8,3)
Answer: SARGASSO SEA
Explanation: Search and rescue by operations leader into nasty gasses across large part of the North Atlantic (8,3)
**SAR** (search and rescue) *by* **O**(perations) [*leader*] *into* ***(gasses)** [anag:*nasty*] +** A** (across) 
 
 
*It's a pity that the clue and solution both have GASS in the same order, making this clue more or less a write-in.