One's penning extremely dreamy lines to create these (6)
I believe the answer is:
idylls
'create these' is the definition.
The definition suggests an adverb but the answer is not.
'one's penning extremely dreamy lines' is the wordplay.
'one's' becomes 'is' (Roman numeral).
'penning' means one lot of letters goes inside another.
'extremely' suggests removing the centre.
'lines' becomes 'll' (I've seen this in other clues**).
'dreamy' with its centre taken out is 'dy'.
'dy'+'ll'='dyll'
'is' placed around 'dyll' is 'IDYLLS'.
'to' is the link.
(Other definitions for idylls that I've seen before include "Short poems descriptive of rural or pastoral life" , "Pastoral pieces" , "Pleasant or romantic scenes from country life" , "Peaceful or romantic scenes or incidents" , "stories of happy innocence" .)