Tars stop, surrounded by snakes (8)

I believe the answer is:

asphalts

'tars' is the definition.
('asphalt' can be a synonym of 'tar')

'stop surrounded by snakes' is the wordplay.
'stop' becomes 'halt' ('halt' can be a synonym of 'stop').
'surrounded by' indicates putting letters inside.
'snakes' becomes 'asps' (asp is a kind of snake).
'halt' inserted into 'asps' is 'ASPHALTS'.

I've seen this clue in The Telegraph.

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