Under most stress, and kind of cross before ordeal (7)
I believe the answer is:
tautest
'under most stress and kind' is the definition.
I can't judge whether this definition defines the answer.
'cross before ordeal' is the wordplay.
'cross' becomes 'tau' (tau cross is a kind of cross).
'before' is a charade indicator (letters next to each other).
'ordeal' becomes 'test' (a testing situation).
'tau'+'test'='TAUTEST'
'of' acts as a link.
Can you help me to learn more?
(Another definition for tautest that I've seen is " Tightest".)