Agreed to welcome fine couples (5)
I believe the answer is:
yokes
'couples' is the definition.
('yoke' can be a synonym of 'couple')
'agreed to welcome fine' is the wordplay.
'agreed' becomes 'yes' ('agreed' can mean 'yes').
'to welcome' indicates putting letters inside (inserted letters are welcomed in).
'fine' becomes 'OK' (synonyms).
'yes' placed around 'ok' is 'YOKES'.
(Other definitions for yokes that I've seen before include "Crosspieces fastened over the necks of a pair of draft animals" , "Oppresses" , "Harnesses together" , "couples" , "Harnesses (oxen)" .)