On the line (2,5)
'on the line' is the definition.
(putting something on the line puts it at stake)
This is the entire clue.
(Other definitions for at stake that I've seen before include "where many martyrs died" , "Being risked, depending on outcome of event" , "Being risked, like money with bookie" , "To be won or lost" , "Being risked or bet on" .)
(Other definitions for atstake that I've seen before include "soon to be Protestant martyr?" , "In danger" .)