Nominally the father of about six? (5)
I believe the answer is:
david
'nominally the' is the definition.
I can't tell whether this defines the answer.
'father of about six?' is the wordplay.
'father of' becomes 'dad' (I can't justify this - if you can you should believe this answer much more).
'about' means one lot of letters goes inside another.
'six?' becomes 'VI' (Roman numerals).
'dad' going around 'vi' is 'DAVID'.
Can you help me to learn more?
(Other definitions for david that I've seen before include "Welsh saint - French painter" , "- Copperfield (Dickens)" , "friend of Jonathan's?" , "Hebrew king" , "Israeli king" .)