Part of rain forest yielding data (4)
I believe the answer is:
info
'data' is the definition.
(information)
'part of rain forest yielding' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'INFO' is hidden within 'rain forest yielding'.
(Other definitions for info that I've seen before include "Data (abbrev.)" , "details" , "Data received and understood (abbr)" , "Gen (abbr)" , "Knowledge (colloq.)" .)