Tree cover perhaps said to generate correspondence (5)
I believe the answer is:
liken
'to generate correspondence' is the definition.
'tree cover perhaps said' is the wordplay.
'tree cover perhaps' becomes 'lichen'.
'said' indicates a 'sounds like' (homophone) clue.
'lichen' is a homophone of 'LIKEN'.
(Other definitions for liken that I've seen before include "Compare" , "Equate" , "Point out the resemblance (to)" , "Represent as similar" .)