One sort of shirt or vest (7)
I believe the answer is:
singlet
'vest' is the definition.
(I know that vest can be written as singlet)
'one sort of shirt' is the wordplay.
'one' becomes 'single' (synonyms).
'sort of shirt' becomes 't' (I've seen this in other clues).
'single'+'t'='SINGLET'
'or' is the link.
(Other definitions for singlet that I've seen before include "Tingles in vest" , "Underwear" , "garment worn by men" , "One unaccompanied" , "Sleeveless vest" .)