Now within reach of solving the riddle (7)
I believe the answer is:
charade
'riddle' is the definition.
(a charade is a puzzle or riddle)
'now within reach of solving' is the wordplay.
I cannot quite see how this works, but
'now' could be 'ad' (AD, Anno Domini, as opposed to BC, Before Christ) and 'ad' is found in the answer.
an anagram of 'reach' is 'chare' which is located in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'the' acts as a link.
Can you help me to learn more?
(Other definitions for charade that I've seen before include "An absurd pretence, or a guessing game" , "Acted riddle - pretence" , "Pretence - travesty" , "Farce - mime" , "Total pretence (as in game)" .)