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 defines the answer.
'who's out of order' is the wordplay.
'who's' becomes 'roy' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'out of' indicates putting letters inside (some letters on the outside of others).
'order' becomes 'om' (Order of Merit).
'roy' enclosing '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" .)