Have about 50 to reduce (5)
I believe the answer is:
halve
'reduce' is the definition.
Although both the answer and definition are verbs in their base form, I don't understand how they can define each other.
'have about 50' is the wordplay.
'about' indicates putting letters inside.
'50' becomes 'l' (Roman numeral).
'have' placed around 'l' is 'HALVE'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for halve that I've seen before include "cut by fifty percent" , "Cut into two equal portions" , "Divide into two equal pieces" , "Bisect" , "Reduce by 50%" .)