Coffee order for vitamin deficiency? (5)
I believe the answer is:
black
'coffee order' is the definition.
(I've seen this in another clue)
'vitamin deficiency?' is the wordplay.
'vitamin' becomes 'b' (B vitamin is an example).
'deficiency?' becomes 'lack' (synonyms).
'b'+'lack'='BLACK'
'for' acts as a link.
(Other definitions for black that I've seen before include "Very darkest colour" , "bar" , "What's written on in the classroom" , "Opponent of nineteen dn (chess)" , "Served without milk" .)