Wearing no shirt, to sum up (2,5)
I believe the answer is:
in short
'to sum up' is the definition.
(I've seen this before)
'wearing no shirt' is the wordplay.
'wearing' is an anagram indicator (wear can mean to become damaged).
'no'+'shirt'='noshirt'
'noshirt' anagrammed gives 'IN SHORT'.
(Other definitions for in short that I've seen before include "Concisely" , "to be brief" , "To sum up, briefly" .)