Was concerned, missing English diamond maybe (4)
I believe the answer is:
card
'diamond maybe' is the definition.
(the diamonds are a playing card suit)
'was concerned missing english' is the wordplay.
'was concerned' becomes 'cared' (I've seen this before).
'missing' indicates named letters should be taken away.
'english' becomes 'e' (abbreviation).
'cared' with 'e' removed is 'CARD'.
(Other definitions for card that I've seen before include "Something players try to avoid" , "Programme of events" , "club perhaps" , "Greetings ----" , "club, for example" .)