Two ducks, one steeped in some orange — it's stickiest (7)
I believe the answer is:
ooziest
'stickiest' is the definition.
(oozy can mean sticky)
'two ducks one steeped in some orange' is the wordplay.
'two ducks' becomes 'oo'.
'one' becomes 'i' (Roman numeral).
'steeped in' is an insertion indicator (I've seen this in other clues).
'some orange' becomes 'zest' (zest from an orange).
'i' going into 'zest' is 'ziest'.
'oo'+'ziest'='OOZIEST'
'it's' is the link.
(Other definitions for ooziest that I've seen before include "most like the mud" , "weeping more than the rest" .)