Professionals have it on toast (6)
I believe the answer is:
prosit
'toast' is the definition.
(I've seen this in another clue)
'professionals have it' is the wordplay.
'professionals' becomes 'pros' ('pro' can be a synonym of 'professional').
'have' means one lot of letters go next to another.
'pros'+'it'='PROSIT'
'on' acts as a link.
(Other definitions for prosit that I've seen before include "I sport with a drinking toast in Germany" , "A German toast - good health" , "Bottoms up (in Germany)" , "Good health! Cheers!" , "All the best" .)