Ran up a share account (9)
I believe the answer is:
narration
'account' is the definition.
(I know that account can be written as narration)
'ran up a share' is the wordplay.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'a share' becomes 'ration' (a ration is a share of a limited resource).
'ran' in reverse letter order is 'nar'.
'nar'+'ration'='NARRATION'
(Other definitions for narration that I've seen before include "Voice-over in film" , "telling" , "Story" , "Spoken account" , "Process of storytelling" .)