Fresh pastry is in short supply (8)
I believe the answer is:
sparsity
'short supply' is the definition.
(I've seen this in another clue)
'fresh pastry is' is the wordplay.
'fresh' is an anagram indicator.
'pastry'+'is'='pastryis'
'pastryis' is an anagram of 'SPARSITY'.
'in' is the link.
(Other definitions for sparsity that I've seen before include "Low density" , "Thinly-scattered state" , "Thinness of occurrence" , "Thinly scattered state" , "Scantiness" .)