At a loose end in spring (4)
I believe the answer is:
free
'spring' is the definition.
(I've seen this in another clue)
'at a loose end in' is the wordplay.
'at' becomes 'fe' (I can't explain this - if you can you should believe this answer much more).
'a loose' becomes 'release' (loose can mean to untie or release).
'end' means to remove the middle letters (I've seen 'ends' mean this).
'in' is an insertion indicator.
'release' with its centre taken out is 're'.
'fe' enclosing 're' is 'FREE'.
Can you help me to learn more?
(Other definitions for free that I've seen before include "Not fixed; not in use" , "See 8" , "Exempt" , "like some public houses" , "without payment" .)