Sort of T-shirt nautical team swill (4,4)
I believe the answer is:
crew neck
'sort of t-shirt nautical' is the definition.
I can't tell whether this definition defines the answer.
'team swill' is the wordplay.
'team' becomes 'crew' (crew is a kind of team).
'swill' becomes 'neck' (I can't explain this - if you can you should believe this answer much more).
'crew'+'neck'='CREW-NECK'
Can you help me to learn more?
(Other definitions for crew neck that I've seen before include "Some wear" , "Close-fitting round jersey opening" , "Round top of a jersey" , "Type of jumper" .)