Salary included fifty for show (4)
I believe the answer is:
play
'show' is the definition.
(play is a kind of show)
'salary included fifty' is the wordplay.
'salary' becomes 'pay' (synonyms).
'included' is an insertion indicator.
'fifty' becomes 'L' (Roman numeral).
'pay' placed around 'l' is 'PLAY'.
'for' acts as a link.
(Other definitions for play that I've seen before include "Freedom of movement" , "Dramatic work" , "Amuse oneself - drama" , "Uncle's premises" , "Work for actors" .)