A tally of twenty (5)
I believe the answer is:
score
This clue is a double definition.
'a tally' is the first definition.
(I've seen this in another clue)
'twenty' is the second definition.
(synonyms)
'of' acts as a link.
(Other definitions for score that I've seen before include "Group of 20" , "Put ball in the net" , "Number of runs" , "Music from film" , "Tally; 20" .)