Economy travellers like these hills! (8)
I believe the answer is:
upgrades
'hills' is the definition.
The definition and answer can be both natural objects as well as being plural nouns.
Maybe there's a link between them I don't understand?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for upgrades that I've seen before include "improvements to software" , "Increases status or improves quality" , "Promotions" .)