Long sort of t-shirt (6)
I believe the answer is:
thirst
'long' is the definition.
(thirst can mean to long or yearn for something)
'sort of t-shirt' is the wordplay.
'sort of' indicates an anagram.
't'+'shirt'='tshirt'
'tshirt' anagrammed gives 'THIRST'.
(Other definitions for thirst that I've seen before include "Dryness" , "Drink to slake it" , "Strong desire for drink" , "lack of water" , "Strong desire from dehydration?" .)