Arranging dates, quick to be loyal (9)
I believe the answer is:
steadfast
'loyal' is the definition.
(I've seen this in another clue)
'arranging dates quick' is the wordplay.
'arranging' indicates an anagram.
'quick' becomes 'fast' (similar in meaning).
'dates' is an anagram of 'stead'.
'stead'+'fast'='STEADFAST'
'to be' is the link.
(Other definitions for steadfast that I've seen before include "Firm, fixed and faithful" , "Constant and resolute" , "Resolutely unwavering" , "Unfaltering" , "Constant; true" .)