Clog of old boy on street caught in groove (8)
I believe the answer is:
'clog' is the definition.
'old boy on street caught in groove' is the wordplay.
'old boy' becomes 'ob'.
'on street' becomes 'st' (I've seen this in other clues).
'caught' becomes 'c' (cricket abbreviation).
'in' indicates putting letters inside.
'groove' becomes 'rut' ('rut' can be a synonym of 'groove').
'c' inserted within 'rut' is 'ruct'.
'of' is the link.
(Other definitions for obstruct that I've seen before include "Check" , "Block the passage or shut out the view" , "Hamper" , "Hinder or impede" , "Get in the way of" .)