Now within reach of solving the riddle (7)
I believe the answer is:
charade
'the riddle' is the definition.
(I've seen this before)
'now within reach of solving' is the wordplay.
I cannot really 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 left over letters.
No letters remain.
This may be the basis of clue (or it may be nonsense).
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)" .)