Cask needing air to remove last of ale (3)
I believe the answer is:
tun
'cask' is the definition.
(I know that tun is a type of cask)
'air to remove last of ale' is the wordplay.
I cannot quite understand how this works, but
'last' could be 't' (I've seen this in other clues) and 't' is found within the answer.
The remaining letters 'un' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'needing' is the link.
Can you help me to learn more?
(Other definitions for tun that I've seen before include "Container of beer" , "Barrel holding many gallons" , "beer barrel" , "Large cask for liquid" , "Nut found in large cask" .)