The Collaborative International Dictionary of English v.0.48:

Clover \Clo"ver\ (kl[=o]"v[~e]r), n. [OE. claver, clover, AS.
   cl[=ae]fre; akin to LG. & Dan. klever, D. klaver, G. klee,
   Sw. kl["o]fver.] (Bot.)
   A plant of different species of the genus Trifolium; as the
   common red clover, Trifolium pratense, the white,
   Trifolium repens, and the hare's foot, Trifolium arvense.
   [1913 Webster]

   Clover weevil (Zool.) a small weevil (Apion apricans),
      that destroys the seeds of clover.

   Clover worm (Zool.), the larva of a small moth (Asopia
      costalis), often very destructive to clover hay.

   In clover, in very pleasant circumstances; fortunate.
      [Colloq.]

   Sweet clover. See Meliot.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "in clover":
   affluent, charmed, comfortable, comfortably situated, content,
   contented, cozy, delighted, easy, eupeptic, euphoric, exhilarated,
   favorably impressed with, glad, gladsome, gratified, in comfort,
   in ease, in good case, in luxury, in velvet, intrigued,
   on Easy Street, on velvet, pleased, pleased as Punch, pleased with,
   prosperous, satisfied, sold on, successful, taken with, thrilled,
   tickled, tickled pink, tickled to death, wealthy