Belated thanks, dry, out of order (5)
I believe the answer is:
tardy
'belated' is the definition.
('tardy' can be a synonym of 'belated')
'thanks dry out of order' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'out of order' is an anagram indicator.
'dry' is an anagram of 'rdy'.
'ta'+'rdy'='TARDY'
(Other definitions for tardy that I've seen before include "Belated" , "Late; sluggish" , "Late - slow" , "Behindhand" , "Unpunctual" .)