People may decline to learn it (5)
I believe the answer is:
latin
'people may' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'decline to learn it' is the wordplay.
I cannot really see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found within the answer.
The remaining letters 'lain' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for latin that I've seen before include "Classical language" , "Old Roman language" , "Romantic language" , "language class" , "Language of old 8 down" .)