Possible Clues:

• low profile
• __ straight face
• ''I couldn't ___ straight face!''
• , 17 Down & 6 Down Betray nothing in tower with a uniform vertical aspect
• Maintain one's composure as warder, say, after row during meal left one a little peeved (4,1,5,5,3)
• -- cool head
• -- low profile
• -- stiff upper lip
• -- straight face
• ___ straight face (don't crack up)