Repress courage under pressure, initially (6,2)
I believe the answer is:
bottle up
'repress' is the definition.
(I've seen this before)
'courage under pressure initially' is the wordplay.
'courage' becomes 'bottle' (bottle can mean courage).
'initially' says to take the initial letters.
The initial letters of 'under pressure' is 'up'.
'bottle'+'up'='BOTTLE UP'
(Other definitions for bottle up that I've seen before include "Keep secret" , "To hold back" , "Repress (eg, feelings)" , "Keep in check" , "Repress, conceal" .)