In speech, scratches part of a sentence (6)
I believe the answer is:
clause
'part of a sentence' is the definition.
(I've seen this before)
'in speech scratches' is the wordplay.
'in speech' shows a homophone (sound like).
'scratches' becomes 'claws' (clawing is a kind of scratching).
'claws' is a homophone of 'CLAUSE'.
(Other definitions for clause that I've seen before include "Section in a contract" , "Grammatical division" , "Separate section of a legal document" , "Verb-carrying component of sentence" , "Separate item in contract" .)