Fish use appendages to move with less effort (5)
I believe the answer is:
skate
I believe this clue is a double definition.
'fish' is the first definition.
(skate is a kind of fish)
'use appendages to move with less effort' is the second definition.
(to use skates or ice skates)
(Other definitions for skate that I've seen before include "current collector" , "Fish of ray family" , "move around ice" , "Runner" , "Travel across ice" .)