Obstruct progress? As well not, perhaps (9)
I believe the answer is:
stonewall
'obstruct progress?' is the definition.
'stonewall' can be an answer for 'obstruct' (stonewalling is a kind of obstructing). I'm not sure about the 'progress?' bit.
'as well not perhaps' is the wordplay.
'perhaps' indicates an anagram.
'as'+'well'+'not'='aswellnot'
'aswellnot' with letters rearranged gives 'STONEWALL'.
Can you help me to learn more?
(Other definitions for stonewall that I've seen before include "Engage in delaying tactics - General Jackson?" , "delay in parliament" , "Use delaying tactics as in cricket" , "Play to defend" , "Check" .)