Higher (6)
'higher' is the definition.
(higher up)
This is all the clue.
(Other definitions for upper that I've seen before include "Pep pill" , "Higher; more northerly" , "The higher of two, berths perhaps" , "Nearer the top" , "Higher in rank" .)
(Other definitions for upward that I've seen before include "Toward a highter place" , "To higher position" , "Towards a higher level" , "Ascending" , "Moving to a higher point" .)
'higher' is the definition.
('tall' can be similar in meaning to 'high')
This is all the clue.
(Other definitions for taller that I've seen before include "Higher in stature" , "Greater in stature" .)