Harsh son, one inspired by a warrior (8)
I believe the answer is:
abrasive
'harsh' is the definition.
(I've seen this before)
'son one inspired by a warrior' is the wordplay.
'son' becomes 's'.
'one' becomes 'i' (Roman numeral).
'inspired by' is an insertion indicator.
'warrior' becomes 'brave' (brave is a kind of warrior).
's'+'i'='si'
'a'+'brave'='abrave'
'si' put inside 'abrave' is 'ABRASIVE'.
(Other definitions for abrasive that I've seen before include "Like pumice - rough in manner" , "Emery paper or steel wool, say" , "Rough to the touch" , "Harsh in manner, capable of causing anger" , "rubbing" .)