Shortage of diamonds on the ground (6)
I believe the answer is:
dearth
'shortage' is the definition.
(dearth can mean a shortage or lack)
'diamonds on the ground' is the wordplay.
'diamonds' becomes 'd' (abbreviation for the card suit diamonds).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'the ground' becomes 'earth' ('earth' can be a synonym of 'ground').
'd'+'earth'='DEARTH'
'of' acts as a link.
(Other definitions for dearth that I've seen before include "Acute shortage" , "Scarcity - lack" , "Scarcity, paucity" , "Lack of resources" , "Severe shortage" .)