Yellow invertebrate (9)
I believe the answer is:
spineless
This clue is a double definition.
'yellow' is the first definition.
(I've seen this before)
'invertebrate?' is the second definition.
(I know that invertebrate can be written as spineless)
(Other definitions for spineless that I've seen before include "Yellow" , "Lily-livered" , "like tattered old book" , "Weak, purposeless" , "Weak, without purpose" .)