Type of ski lift (4)
'type of ski lift' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for t-bar that I've seen before include "Type of ski lift" , "Type of ski-lift" , "Towing ski lift" , "Type of towing lift for skiers" , "that provides lifts?" .)
(Another definition for tbar that I've seen is " Tower, perhaps".)