Play involving black fellow (4)
I believe the answer is:
toby
'fellow' is the definition.
(I've seen this before)
'play involving black' is the wordplay.
'play' becomes 'toy' (synonyms).
'involving' means one lot of letters goes inside another.
'black' becomes 'b' (as in pencil classifications).
'toy' going around 'b' is 'TOBY'.
(Other definitions for toby that I've seen before include "Member of the 12 [SHANDY] family" , "fellow" , "Mr Punch's dog, beer-jug" , "Belch, perhaps" , "Kind of jug" .)