Convert to it in a pub -- 'The Slaughterhouse' (8)
I believe the answer is:
abattoir
'the slaughterhouse' is the definition.
('abattoir' can be a synonym of 'slaughterhouse')
'convert to it in a pub' is the wordplay.
'convert' indicates anagramming the letters (I've seen this in other clues).
'in' indicates putting letters inside.
'pub' becomes 'bar' (I've seen this before).
'to'+'it'='toit'
'toit' anagrammed gives 'ttoi'.
'a'+'bar'='abar'
'ttoi' put into 'abar' is 'ABATTOIR'.
(Other definitions for abattoir that I've seen before include "place where animals die" , "[EASY MEAT] half-cut seen here?" , "it makes a killing" , "scene of slaughter" , "shambles once" .)