Obstructs the security devices in a pub, maybe (6,2)

'obstructs' is the definition.
(blocking up is a kind of obstructing)

'security devices in a pub maybe' is the wordplay.
'security devices' becomes 'locks' (I've seen this in another clue).
'in' means one lot of letters goes inside another.
'maybe' indicates anagramming the letters.
'pub' with letters rearranged gives 'bup'.
'locks' put within 'bup' is 'BLOCKS UP'.

'the' is the link.