Expression clashes in speech (6)
I believe the answer is:
phrase
'expression' is the definition.
(phrase is a kind of expression)
'clashes in speech' is the wordplay.
'clashes' becomes 'frays'.
'in speech' shows a homophone (sound like).
'frays' sounds like 'PHRASE'.
(Other definitions for phrase that I've seen before include "partial sentence" , "Articulate, couch" , "Saying" , "Present" , "Sequence of words" .)