Snake given by important person to the queen (5)
I believe the answer is:
viper
'snake' is the definition.
(I know that viper is a type of snake)
'by important person to the queen' is the wordplay.
'by' means one lot of letters go next to another.
'important person' becomes 'vip' (VIP is an example).
'to the queen' becomes 'ER' (Elizabeth Regina ie Queen Elizabeth).
'vip' put next to 'er' is 'VIPER'.
'given' is the link.
(Other definitions for viper that I've seen before include "A poisonous snake or treacherous person" , "Venomous snake, person" , "A small poisonous snake" , "Malicious person" , "spiteful person" .)