Crustacean with seven pairs of legs (6)
I believe the answer is:
isopod
'crustacean with seven pairs of legs' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for isopod that I've seen before include "Crustacean with seven pairs of legs for crawling" , "small crustacean" , "Member of an order of crustaceans" , "Slater, for instance" , "This crusty creature" .)