to lack any experience of a particular activity.

I'd never interviewed anyone on television before. I was new to the game and needed all the advice I could get.

• at least
• at leisure
• at length
• at liberty
• at loggerheads
• at long last
• at loose ends
• at low ebb
• at most
• at mother's knee
• at no time
• at odds
• at odds with
• at odds with someone
• at odds with something
• at once
• at one fell swoop
• at one sitting
• at one time
• at one time or another
• a tongue-lashing
• a toss-up
• a tough act to follow
• a tough cookie
• a tough nut