Nothing fresh in stable block (9)
I believe the answer is:
stonewall
'block' is the definition.
(stonewalling is a kind of blocking)
'nothing fresh in stable' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'fresh' becomes 'new' ('new' can be a synonym of 'fresh').
'in' is an insertion indicator.
'stable' becomes 'stall' (I've seen this in other clues).
'o'+'new'='onew'
'onew' inserted inside 'stall' is 'STONEWALL'.
(Other definitions for stonewall that I've seen before include "Check" , "Obstruct by refusing to answer questions" , "Delay or block (a proposal's) progress" , "Use delaying tactics as in cricket" , "Refuse to co-operate" .)