Polluted seas filled with sticky stuff for all time (7)
I believe the answer is:
ageless
'for all time' is the definition.
(belonging to all ages)
'polluted seas filled with sticky stuff' is the wordplay.
'polluted' is an anagram indicator.
'filled with' means one lot of letters goes inside another.
'sticky stuff' becomes 'gel' (sticky substance).
'seas' is an anagram of 'aess'.
'aess' placed around 'gel' is 'AGELESS'.
(Other definitions for ageless that I've seen before include "Enduring" , "Ever young" , "Lasting forever" , "Small amphibian" , "not getting on" .)