Smelly new diet at the welfare centre (5)
I believe the answer is:
fetid
'smelly' is the definition.
('fetid' can be a synonym of 'smelly')
'new diet at the welfare centre' is the wordplay.
'new' indicates anagramming the letters.
'at' says to put letters next to each other (I've seen this in other clues).
'centre' indicates the central letters.
The middle letter of 'welfare' is 'f'.
'diet' with letters rearranged gives 'etid'.
'etid' put after 'f' is 'FETID'.
(Other definitions for fetid that I've seen before include "Smelling bad, stinking" , "Malodorous, stinking" , "Putrid and stinking" , "Stinking, rank" , "Stinking, perhaps breath" .)