How numbers of letters appear here to bring up one demand they oddly put about (15)
I believe the answer is:
parenthetically
'about' is the definition.
Both the answer and definition are adverbs. Perhaps they are linked in a way I don't understand?
'how numbers of letters appear here to bring up one demand they oddly' is the wordplay.
I cannot really see how this works, but
'here' could be 'ent' (I've seen this in other clues) and 'ent' is found within the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
'demand' could be 'call' (call is a kind of demand) and 'call' is found within the answer.
an anagram of 'they' is 'hety' which is located in the left over letters.
The remaining letters 'par' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'put' acts as a link.
Can you help me to learn more?
(Other definitions for parenthetically that I've seen before include "(sic)" , "as an aside" , "A number here may appear this way!" .)