He’ll be about fifty to the good (5)
I believe the answer is:
bloke
'he'll' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'be about fifty to the good' is the wordplay.
'about' means one lot of letters goes inside another.
'fifty' becomes 'l' ('L' can be a synonym of 'fifty').
'to the good' becomes 'ok'.
'l'+'ok'='lok'
'be' going around 'lok' is 'BLOKE'.
Can you help me to learn more?
(Other definitions for bloke that I've seen before include "British fellow or chap" , "Chap, lad" , "Geezer" , "Fellow (informal)" , "Chap, man" .)