Imagine vines developing with time (8)
I believe the answer is:
envisage
'imagine' is the definition.
('envisage' can be a synonym of 'imagine')
'vines developing with time' is the wordplay.
'developing' is an anagram indicator.
'with' means one lot of letters go next to another.
'time' becomes 'age' (age is a kind of time).
'vines' is an anagram of 'envis'.
'envis'+'age'='ENVISAGE'
(Other definitions for envisage that I've seen before include "Imagine, foresee" , "Form a mental image of" , "Consider, contemplate" , "Contemplate, imagine" , "Picture in one's mind" .)