It may hurt a little at closing time (4)
I believe the answer is:
bite
'it may hurt a' is the definition.
The definition suggests a singular noun which matches the answer.
'little at closing time' is the wordplay.
'little' becomes 'bit' (I've seen this in another clue).
'at' says to put letters next to each other.
'closing time' becomes 'e' (I am not sure about this - if you are sure you should believe this answer much more).
'bit'+'e'='BITE'
Can you help me to learn more?
(Other definitions for bite that I've seen before include "Quick snack" , "Get teeth into" , "champ" , "Small amount of food" , "Grip; take effect" .)