Cover the cooking-vessel up (3)
I believe the answer is:
top
'cover' is the definition.
(I know that cover can be written as top)
'cooking-vessel up' is the wordplay.
'cooking vessel' becomes 'pot' (I've seen this before).
'up' is a reversal indicator (in down clue: letters go upwards).
'pot' written backwards gives 'TOP'.
'the' is the link.
(Other definitions for top that I've seen before include "Crown" , "Peak; child's toy" , "Highest point or position" , "Zenith" , "cap and > sweater" .)