Garment ordeal oddly involving a shirt (7)
I believe the answer is:
leotard
'garment' is the definition.
(I've seen this before)
'ordeal oddly involving a shirt' is the wordplay.
'oddly' indicates an anagram.
'involving' indicates putting letters inside.
'a shirt' becomes 't' (as in a T-shirt).
'ordeal' anagrammed gives 'leoard'.
'leoard' placed around 't' is 'LEOTARD'.
(Other definitions for leotard that I've seen before include "Ballet outfit" , "One-piece garment worn by acrobat" , "Close-fitting garment worn by dancers" , "Body suit for dancers" , "Dancers might wear this" .)