Brief season leads to deficit (9)
I believe the answer is:
shortfall
'deficit' is the definition.
(synonyms)
'brief season' is the wordplay.
'brief' becomes 'short' (similar in meaning).
'season' becomes 'fall' (alternative name for autumn).
'short'+'fall'='SHORTFALL'
'leads to' is the link.
(Other definitions for shortfall that I've seen before include "what we're lacking" , "Not quite what's expected" , "Deficiency" , "Deficit of something required" , "Not enough money" .)