Modified spears are in short supply (6)
I believe the answer is:
sparse
'in short supply' is the definition.
(sparse can mean meagre or minimal)
'modified spears' is the wordplay.
'modified' indicates an anagram.
'spears' anagrammed gives 'SPARSE'.
'are' is the link.
(Other definitions for sparse that I've seen before include "Thinly scattered, not dense" , "In short supply" , "Thinly-spread" , "rarely occurring" , "Thinly dispersed" .)