It’s hard being a former party leader (5)
I believe the answer is:
steel
This might be a double definition.
'it's hard' is the first definition.
'a former party leader' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'being' acts as a link.
Can you help me to learn more?
(Other definitions for steel that I've seen before include "brace" , "Structural metal alloy" , "Make hard and unfeeling" , "The staying power" , "Form of iron" .)