Cross as partygoers seen in outskirts of Tonbridge (8)
I believe the answer is:
traverse
'cross' is the definition.
(synonyms)
'partygoers seen in outskirts of tonbridge' is the wordplay.
'partygoers' becomes 'ravers' (people attending a rave).
'seen in' is an insertion indicator.
'outskirts of' means to remove the middle letters.
'tonbridge' with its centre taken out is 'te'.
'ravers' put within 'te' is 'TRAVERSE'.
'as' acts as a link.
(Other definitions for traverse that I've seen before include "In mountaineering, a steep slope to be crossed from side to side" , "Cross sideways" , "Travel across or pass over" , "Move across" , "cover" .)