Invertebrate chicken? (9)

I believe the answer is:

spineless

This clue is a double definition.

'invertebrate' is the first definition.
(thesaurus)

'chicken?' is the second definition.
(thesaurus)

(Other definitions for spineless that I've seen before include "Lily-livered" , "like tattered old book" , "Cowardly, lacking backbone" , "Weak, purposeless" , "Craven, lacking vertebrae" .)

I've seen this clue in The Telegraph.

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