It's smart to avoid being at a loose end (4)
I believe the answer is:
cute
'it's smart' is the definition.
(I've seen this before)
'avoid being at a loose end' is the wordplay.
'avoid being' becomes 'cut' (I can't explain this - if you can you should believe this answer much more).
'at' is a charade indicator (letters next to each other).
'end' suggests the final letters.
The final letter of 'loose' is 'e'.
'cut'+'e'='CUTE'
'to' is the link.
Can you help me to learn more?
(Other definitions for cute that I've seen before include "Pretty or cunning" , "Pretty and attractive" , "Precious" , "Daintily pleasing" , "Delightfully pretty or dainty" .)