Throw small, uncovered, tailless reptile (11)
I believe the answer is:
rattlesnake
'reptile' is the definition.
(type of snake)
'throw small uncovered tailless' is the wordplay.
'throw' becomes 'rattle' (I've seen this before).
'small' becomes 's' (abbreviation - e.g. clothes size).
'uncovered' becomes 'naked' (I've seen this in another clue).
'tailless' means to remove the last letter (the tail of the word is removed).
'naked' with its last letter taken away is 'nake'.
'rattle'+'s'+'nake'='RATTLESNAKE'
(Other definitions for rattlesnake that I've seen before include "Virulent type" , "Poisonous creature" , "Heavy-bodied American pit viper" , "Sidewinder" , "Venomous creature" .)