Roll up one's sleeves, we hear, to show what all across answers do here (4,4)
I believe the answer is:
bear arms
'all across answers do here' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'roll up one's sleeves we hear to show' is the wordplay.
I cannot really understand how this works, but
'sleeves' could be 'arms' ('arm' can be a synonym of 'sleeve') and 'arms' is present in the answer.
'show' could be 'bear' (I've seen this before) and 'bear' is found in the answer.
No letters remain.
This explanation may well be incorrect...
'what' is the link.
Can you help me to learn more?
(Other definitions for bear arms that I've seen before include "Serve as a soldier" , "Serve in the forces" , "right for American?" , "Carry weapons" , "they may be used in a tight squeeze!" .)