Smart spot to take a short sleep in (6)
I believe the answer is:
snappy
'smart' is the definition.
(snappy can mean smartly dressed)
'spot to take a short sleep in' is the wordplay.
'spot' becomes 'spy' (synonyms).
'to take' indicates putting letters inside (inserted letters are taken in).
'a short sleep in' becomes 'nap' (I can't explain this - if you can you should believe this answer much more).
'spy' placed around 'nap' is 'SNAPPY'.
Can you help me to learn more?
(Other definitions for snappy that I've seen before include "Short-tempered" , "sort of dresser" , "bad tempered" , "Instantaneous" , "Irritable - smart" .)