Generously accommodating a chap who's out of order (5)
I believe the answer is:
roomy
'generously accommodating a chap' is the definition.
I can't judge whether this definition defines the answer.
'who's out of order' is the wordplay.
'who's' becomes 'roy' (I can't justify this - if you can you should believe this answer much more).
'out of' is an insertion indicator (some letters on the outside of others).
'order' becomes 'om' (Order of Merit).
'roy' going around 'om' is 'ROOMY'.
Can you help me to learn more?
(Other definitions for roomy that I've seen before include "so wide" , "Spacious, can swing a cat in it" , "Spaced-out" , "Capacious" , "Without cramping" .)