if you field a team, an army etc, they represent you or fight for you in a competition, election, or war:
The Ecology Party fielded 109 candidates.
We fielded a team of highly talented basketball players.
to answer questions, telephone calls etc, especially when there are a lot of them or the questions are difficult:
The Minister fielded questions on the Middle East.
The press office fielded numerous calls from the media.
the team that is fielding in a game of cricket or baseball is the one that is throwing and catching the ball, rather than the one hitting it [≠ be batting]
if you field the ball in a game of cricket or baseball, you stop it after it has been hit