Silk cut completely the wrong way (8)
I believe the answer is:
prunella
'silk' is the definition.
(I have seen 'Strong silk ' mean 'prunella' so perhaps 'silk' could also mean 'prunella')
'cut completely the wrong way' is the wordplay.
'cut' becomes 'prune' (synonyms).
'completely' becomes 'all' (synonyms).
'the wrong way' is a reversal indicator.
'all' reversed gives 'lla'.
'prune'+'lla'='PRUNELLA'
(Other definitions for prunella that I've seen before include "Strong silk" , "It reputedly heals everyone" , "flower" , "Scales maybe" , "-- Scales, actress" .)