Afraid there's the devil to pay out! (7)
I believe the answer is:
panicky
'afraid' is the definition.
(similar in meaning)
'the devil to pay out' is the wordplay.
'the devil' becomes 'nick' (Nick and Old Nick are names for the Devil).
'out' means one lot of letters goes inside another.
'nick' placed inside 'pay' is 'PANICKY'.
'there's' is the link.
(Other definitions for panicky that I've seen before include "(Irrationally) fearful" , "nervous!" , "Inclined to lose head" , "Very worried" , "in a tizzy" .)