United tie, letting in own goal (8)
I believe the answer is:
together
'united' is the definition.
(thesaurus)
'tie letting in own goal' is the wordplay.
'tie' becomes 'tether' (I've seen this before).
'letting in' is an insertion indicator.
'own goal' becomes 'og' (football abbreviation).
'tether' enclosing 'og' is 'TOGETHER'.
(Other definitions for together that I've seen before include "Concertedly" , "In one another's company" , "United; touching" , "tied" , "Got there (anag.)" .)