Warning given to cowardly character (6,4)
I believe the answer is:
yellow card
'warning' is the definition.
(I've seen this before)
'given to cowardly character' is the wordplay.
'given to' says to put letters next to each other.
'cowardly' becomes 'yellow' (yellow can informally mean cowardly).
'character' becomes 'card' (both can mean a humorous person).
'yellow'+'card' is 'YELLOW CARD'.
(Other definitions for yellow card that I've seen before include "Warning to footballer" , "Warning leading to temporary dismissal" , "Warning to footballers" , "With which a referee cautions player" , "Footballer's caution" .)