Bloke in room a Neanderthal (3)
I believe the answer is:
man
'bloke' is the definition.
(informal term for a man)
'in room a neanderthal' is the wordplay.
'in' says the answer is hidden in the clue.
'MAN' can be found hidden inside 'room a neanderthal'.
(Other definitions for man that I've seen before include "Isle of . . ., . . . o' war" , "Provide with crew" , "Chap" , "just one" , "Fellow" .)