Procedure involves returning how crass! (4)
I believe the answer is:
rude
'crass' is the definition.
(I've seen this in another clue)
'procedure involves returning' is the wordplay.
'involves' indicates a hidden word.
'returning' is a reversal indicator.
'edur' can be found hidden inside 'procedure'.
'edur' in reverse letter order is 'RUDE'.
'how' acts as a link.
(Other definitions for rude that I've seen before include "Impolite or coarse" , "Uncivil" , "so curt here?" , "Unmannerly" , "having no manners?" .)