Repeat attire accidentally worn by me at last (7)
I believe the answer is:
iterate
'repeat' is the definition.
(synonyms)
'attire accidentally worn by me at last' is the wordplay.
'accidentally' indicates anagramming the letters (a chaotic or accidental ordering of the letters).
'worn by' means one lot of letters goes inside another (I've seen this in other clues).
'at last' indicates one should take the final letters.
The last letter of 'me' is 'e'.
'attire' is an anagram of 'itrate'.
'itrate' enclosing 'e' is 'ITERATE'.
(Other definitions for iterate that I've seen before include "Recapitulate" , "Repeat, state again" , "State repeatedly, say again" , "Utter or perform repeatedly" , "Say again, repeat" .)