Scientist puts whiskey in drain mistakenly (6)
I believe the answer is:
darwin
'scientist' is the definition.
(Darwin is an example)
'whiskey in drain mistakenly' is the wordplay.
'whiskey' becomes 'W' (alpha bravo charlie delta ...).
'in' is an insertion indicator.
'mistakenly' indicates anagramming the letters.
'drain' anagrammed gives 'darin'.
'w' put within 'darin' is 'DARWIN'.
'puts' acts as a link.
(Other definitions for darwin that I've seen before include "He propounded the Theory of Evolution" , "Aus. N. Territory capital" , "Charles . . . . . ., author of 'The Origin of Species'" , "Evolution theorist" , "Natural scientist and Australian city" .)