This restricts the learner to singly copy (10)
I believe the answer is:
limitation
'this restricts the learner' is the definition.
The definition suggests a singular noun which matches the answer.
'singly copy' is the wordplay.
'singly' becomes 'l' (I can't explain this - if you can you should give a lot more credence to this answer).
'copy' becomes 'imitation' (imitation is a kind of copy).
'l'+'imitation'='LIMITATION'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for limitation that I've seen before include "Check" , "Shortcoming" , "lack of talent" , "Rule restricting extent" , "lack of ability" .)