Can I fight a monster during charity?
From the rules "When To Play Cards" (page 5):


  Monsters 
  
  If drawn face-up, during the “Kick Open The Door” phase, they
  immediately attack the person who drew them. If acquired any other
  way, they go into your hand and may be played during “Looking For
  Trouble,” or played on another player with the Wandering Monstercard.


Monster cards can only be played during the "Kick Open The Door" phase or by other cards like Wandering Monster which explicitly allow them to be played. Thus you cannot simply play and fight them prior to charity. 

Theoretically if you happened to also be holding a card that allowed you to play a monster as part of its effect, then you could play that card and the monster, depending on the conditions of the card. For instance, Wandering Monster itself doesn't help here as it is played on a player already in combat, but there could come along a new card someday (or there could be one in some expansion I don't have) that could allow it.