Are they hard to hit on the head? (5)
I believe the answer is:
nails
'are they' is the definition.
The definition suggests a plural noun which matches the answer.
'hard to hit on the head?' is the wordplay.
'hard' becomes 's' (I can't justify this - if you can you should give a lot more credence to this answer).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'hit on the head?' becomes 'nail' (I've seen this in another clue).
's' put after 'nail' is 'NAILS'.
Can you help me to learn more?
(Other definitions for nails that I've seen before include "Metal fasteners" , "Fastens with spikes" , "Claws" , "Talons" , "Horny plates and pointed pins" .)