Joy to behold finally, a grandmaster (4)
I believe the answer is:
yoda
'grandmaster' is the definition.
(Jedi master in the Star Wars films)
'joy to behold finally a' is the wordplay.
'finally' says to take the final letters.
The last letters of 'joy to behold' are 'yod'.
'yod'+'a'='YODA'
(Other definitions for yoda that I've seen before include "one with idiosyncratic syntax" , "Green being" , "Grand Master of the Jedi Order" .)