Learn to use gravity on incline (5)
I believe the answer is:
glean
'learn' is the definition.
(thesaurus)
'gravity on incline' is the wordplay.
'gravity' becomes 'g'.
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'incline' becomes 'lean' (synonyms).
'g'+'lean'='GLEAN'
'to use' acts as a link.
(Other definitions for glean that I've seen before include "Collect gradually from scattered sources" , "Garner" , "Gather (grains of information?)" , "Gather (after reapers)" , "Angel (anag.)" .)