Both arduous and difficult inside (4)
I believe the answer is:
hard
'difficult inside' is the definition.
Both the definition and answer are adjectives. Perhaps there's a link between them I don't understand?
'both arduous' is the wordplay.
'HARD' is hidden in amongst the letters.
However, I'm not sure how this is indicated.
'and' acts as a link.
Can you help me to learn more?
(Other definitions for hard that I've seen before include "Firm; demanding; stern" , "Complicated" , "Difficult - firm" , "Firm, rigid, road leading to foreshore" , "Difficult; severe" .)