Drop in to see a hand? (4)
I believe the answer is:
'drop in' is the definition.
(I've seen this in another clue)
'see a hand?' is the wordplay.
'see' becomes 'C' (the word for the letter, according to Chambers).
'a hand?' becomes 'all' (I can't explain this - if you can you should give a lot more credence to this answer).
'c'+'all'='CALL'
'to' is the link.
Can you help me to learn more?
(Other definitions for call that I've seen before include "Pay a visit" , "Cry - summon" , "Visit; cry out" , "Telephone - give a name" , "Entitle" .)