Initially reels out old scores to settle (5)
I believe the answer is:
roost
'settle' is the definition.
(I know that roost is a more specific form of settle)
'initially reels out old scores to' is the wordplay.
'initially' indicates taking the first letters.
The initial letters of 'reels out old scores to' is 'ROOST'.
(Other definitions for roost that I've seen before include "Thin paper" , "Glowing with joy" , "Hen's resting place" , "Perch on a branch" , "residence" .)