Garment starts to squeeze him... it's really tight (1-5)
I believe the answer is:
t-shirt
'garment' is the definition.
(I know that t-shirt is a type of shirt)
'starts to squeeze him it's really tight' is the wordplay.
'starts' says to take the initial letters.
The initial letters of 'to squeeze him its really tight' is 'T-SHIRT'.
(Other definitions for t-shirt that I've seen before include "Collarless pullover shirt" , "Light garment for upper body, often with pictures or slogan" , "Informal collarless top" , "Casual short-sleeved top" , "Casual upper garment" .)