Surprises in a street when meeting dogs with no lead (8)

'surprises' is the definition.
(astounding is a kind of surprising)

'when meeting dogs with no lead' is the wordplay.
'when meeting' becomes 'ast' (I can't justify this - if you can you should believe this answer much more).
'dogs' becomes 'hounds' ('hound' can be a synonym of 'dog').
'with no lead' means to remove the first letter.
'hounds' with its first letter taken off is 'ounds'.
'ast'+'ounds'='ASTOUNDS'

'in a street' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.

Can you help me to learn more?