Cowardly eccentric shows caution (6,4)
I believe the answer is:
yellow card
'caution' is the definition.
(caution given to a footballer)
'cowardly eccentric' is the wordplay.
'cowardly' becomes 'yellow' (similar in meaning).
'eccentric' becomes 'card' (I've seen this before).
'yellow'+'card'='YELLOW CARD'
'shows' is the link.
(Other definitions for yellow card that I've seen before include "With which a referee cautions player" , "Warning to footballers" , "Warning to footballer" , "Footballer's caution" , "Warning leading to temporary dismissal" .)