Stay under the covers finishing popular fiction
I believe the answer is:
lie in
'stay' is the definition.
The answer and definition can be both to do with fundamental existence as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?
'under the covers finishing popular fiction' is the wordplay.
I cannot quite see how this works, but
'popular' could be 'in' and 'in' is present in the answer.
'fiction' could be 'lie' (I've seen this before) and 'lie' is found in the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lie in that I've seen before include "delay rise" , "An extended stay in bed" , "Extended snooze" , "Prolonged bed rest" , "rest of the morning" .)