There's a girl for every one, even a snake! (5)
I believe the answer is:
viper
'snake' is the definition.
(I know that snake can be written as Viper)
'there's a girl for every' is the wordplay.
'there's a girl' becomes 'vi' (short for Violet).
'for every' becomes 'per' ('per' means 'for each' or 'for every').
'vi'+'per'='VIPER'
'one even a' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for viper that I've seen before include "Venomous snake, person" , "crawler" , "spiteful person" , "Malicious person" , "A small poisonous snake" .)