They're most likely asking for
Endure, a buff that increases your HP and SP for an hour and can be cast outside of party. Clerics may feel that they only truly become Clerics when they reach level 47 and are able to give this buff. They may even go around for hours randomly-buffing strangers. *cough*
Other alternative is
Immune, one-hour buff that increases resistance to poison and disease. Much less likely to be the buff they're hoping for, but it's welcome nonetheless.
Threaded Mode