Display bill: it’s a critical moment (10)
I believe the answer is:
flashpoint
'it's a critical moment' is the definition.
(a flashpoint is an important moment)
'display bill' is the wordplay.
'display' becomes 'flash' (flashing is a kind of displaying).
'bill' becomes 'point' (bill can mean a point or promontory).
'flash'+'point'='FLASHPOINT'
(Other definitions for flashpoint that I've seen before include "moment of emergency" , "Moment when hostility flares up" .)