Collarless shirt (3)
I believe the answer is:
tee
'collarless shirt' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tee that I've seen before include "Golfing equipment" , "Starting place for a golfer" , "Drive off it, half-tittering" , "Golfer's peg" , "Golf starting point" .)