Use for what?
As loof said - leave the ArenA for LF3 if you're planning to play it too (and I recommend to do that!!!!!

)
And if you really want to have the Solblast Rod - just level up Cindy, equip her with Primo Hat and stuff that boosts speed and finally use speed boostings spells on her (like Tarbulla's Energy Burn).
I think she needs about 1200SP to steal what's inside the chest at the Mage Guild.