Gone astray, I have picked up old clothes (8)
I believe the answer is:
'gone astray' is the definition.
(to deviate from something is to go astray from it)
'i have picked up old clothes' is the wordplay.
'i have' becomes 'I've' (contraction of 'I have').
'picked up' shows that the letters should be reversed in order.
'old' becomes 'dated' (dated can mean old or out of date).
'clothes' indicates putting letters inside (inserted letters are clothed in others).
'ive' reversed gives 'evi'.
'evi' put within 'dated' is 'DEVIATED'.
(Other definitions for deviated that I've seen before include "Diverged from expected course" , "Turned away from an expected course" , "Turned aside" .)