Uncovering line, refers to prompts (7)
I believe the answer is:
incites
'prompts' is the definition.
('incite' can be a synonym of 'prompt')
'uncovering line refers to' is the wordplay.
'uncovering' means to look at the middle letters.
'refers to' becomes 'cites' ('cite' can be a synonym of 'refer to').
The middle of 'line' is 'in'.
'in'+'cites'='INCITES'
(Other definitions for incites that I've seen before include "Eggs on" , "Encourages" , "Provokes or stirs up" , "Provokes to action" .)