Vessel surprisingly dark brown at the top (7)
I believe the answer is:
tankard
'vessel' is the definition.
(tankard is a kind of vessel)
'surprisingly dark brown at the top' is the wordplay.
'surprisingly' is an anagram indicator.
'brown' becomes 'tan' (tan is a kind of brown).
'at the top' means one lot of letters go next to another.
'dark' is an anagram of 'kard'.
'kard' put after 'tan' is 'TANKARD'.
(Other definitions for tankard that I've seen before include "Drinking vessel with a handle" , "Large drinking vessel" , "A drinking mug with handle" , "One-handled beer mug" , "One-handled drinking mug" .)