Creepy type calls, mostly having nothing on! (4,5)

'creepy type' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

'calls mostly having nothing on' is the wordplay.
'calls' becomes 'rings' ('ring' can be a synonym of 'call').
'mostly' means to remove the last letter.
'having nothing on' becomes 'snake' (I can't justify this - if you can you should give a lot more credence to this answer).
'rings' with its final letter taken away is 'ring'.
'ring'+'snake'='RING SNAKE'

Can you help me to learn more?