In arrears, graduate banker is at last jailed (6,4)
I believe the answer is:
behind bars
'jailed' is the definition.
(I've seen this in another clue)
'in arrears graduate banker is at last' is the wordplay.
'in arrears' becomes 'behind' (I've seen this before).
'graduate' becomes 'BA' (someone with a Bachelor of Arts degree).
'at last' says to take the final letters.
The last letters of 'banker is' are 'rs'.
'behind'+'ba'+'rs'='BEHIND BARS'
(Other definitions for behind bars that I've seen before include "Serving time" , "Doing porridge" , "tapsters" , "Like staff serving drinks" , "like some of the hotel staff?" .)