There are several examples of "s" words that are similar in meaning to "clever," but they do have different connotations associated with them. For instance, snark, which carries a somewhat negative meaning. On the other hand, sharp, has a much more positive meaning.
Another word for opportunity which begins with 'S' is scope.
softening
Scrap.
Steam
One word would be "prince". Add an -s and you have the plural - "princes". Add another -s and you have "princess", a word in singular form.
Another word for opportunity which begins with 'S' is scope.
synopsis
Side-Street
Substitute.
softening
sojourn
spousal
Sort or Savor
stole
source spring square
My thesaurus lists stick or stab. The noun "lance" is related to spear.
smart