Long crumpled T-shirt (6)
I believe the answer is:
thirst
'long' is the definition.
(thesaurus)
'crumpled t-shirt' is the wordplay.
'crumpled' indicates anagramming the letters.
't'+'shirt'='tshirt'
'tshirt' with letters rearranged gives 'THIRST'.
(Other definitions for thirst that I've seen before include "Want of drink" , "The inducement for 5 Down" , "Physiological need to drink" , "lack of water" , "T-shirt (anag)" .)