Concerned with ousting bad smell from fish tank component (6)
I believe the answer is:
turret
'tank component' is the definition.
(part of a military tank)
I cannot understand how the rest of the clue works.
(Other definitions for turret that I've seen before include "One of two rings" , "Small tower projecting from a wall of a castle" , "Armoured tower" , "Small tower on defensive wall - or tank" , "Small corner tower" .)