Obstruct, confine or stifle (6)
I believe the answer is:
dampen
'stifle' is the definition.
(I know that stifle can be written as dampen)
'obstruct confine' is the wordplay.
'obstruct' becomes 'dam' (damming is a kind of obstructing).
'confine' becomes 'pen' (I've seen this in another clue).
'dam'+'pen'='DAMPEN'
'or' is the link.
(Other definitions for dampen that I've seen before include "get a bit wet" , "Moisten" , "Make slightly moist, or discourage" , "Stifle" , "Make moist or depressed" .)