Long and badly cut T-shirt (6)
I believe the answer is:
thirst
'long' is the definition.
(thirst can mean to long or yearn for something)
'cut t-shirt' is the wordplay.
'cut' indicates an anagram (cut can mean mixed).
't'+'shirt'='tshirt'
'tshirt' with letters rearranged gives 'THIRST'.
'and badly' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for thirst that I've seen before include "Quaff to slake it" , "Strong need for drink" , "A need (for liquid)" , "Long" , "Strong desire for something" .)