Rather crude bitter? A familiar complaint (6)
'a familiar complaint' is the definition.
'rather crude bitter?' is the wordplay.
'rather crude' becomes 'common'.
'bitter?' becomes 'cold' ('cold' can be similar in meaning to 'bitter').
'common'+'cold'='COMMON COLD'
(Other definitions for common cold that I've seen before include "Regular winter illness" , "Mild viral infection" .)
'rather crude' is the definition.
I cannot understand how the remainder of the clue works.
(Other definitions for common that I've seen before include "Met with frequently" , "Open land; not rare" , "Usual, of no particular distinction" , "Ill-bred, not refined in manner" , "Ordinary, not refined" .)