Arduous (4)
'arduous' is the definition.
(synonyms)
This is all the clue.
(Other definitions for hard that I've seen before include "impenetrable" , "Difficult - firm" , "Resentment" , "Complicated" , "Solid, firm, rigid" .)
'arduous' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for uphill that I've seen before include "Towards a slope's top" , "Difficult, like steep slope" , "Inclined" , "Sloping upwards" , "This going is tough, but climb on" .)