Bet a blow sadly overwhelms area in a weak state (2,1,3,3)
I believe the answer is:
at a low ebb
'in a weak state' is the definition.
(I've seen this before)
'bet a blow sadly overwhelms area' is the wordplay.
'sadly' indicates anagramming the letters.
'overwhelms' means one lot of letters goes inside another.
'area' becomes 'a' (maths abbreviation).
'bet'+'a'+'blow'='betablow'
'betablow' with letters rearranged gives 'atlowebb'.
'atlowebb' going around 'a' is 'AT A LOW EBB'.
(Other definitions for at a low ebb that I've seen before include "In a weak state" , "Dispirited" , "In a poor state" , "temporarily down" , "In recession" .)