Supplied grass skirts to be softened (8)
I believe the answer is:
relented
'softened' is the definition.
('relent' can be a synonym of 'soften')
'supplied grass skirts' is the wordplay.
'supplied' becomes 'lent'.
'grass' becomes 'reed' (I've seen this before).
'skirts' is an insertion indicator.
'lent' going into 'reed' is 'RELENTED'.
'to be' is the link.
(Other definitions for relented that I've seen before include "Became less intense" , "Gave in (to pleas?)" , "thought better of it" , "Grew less severe" , "Give in (to pleas?)" .)