Explanation

If the clerk treats his “office” (a fancy way to say his “job”) with a general lack of respect, then he treats his clients with a similarly cool and distant manner, a manner of casual nonchalance. Note that the other two possibilities do not fit at all (meticulousness would be positive, and envy is not indicated by the sentence). As for the second blank, knowing that “grand farce” is a common English idiom is helpful but is not essential—the word farce, or “mockery,” is the only word that fits. ##

A grand gesture would be positive (a grand gesture would be something like an elaborate marriage proposal, apology, etc.), and there is no clue that the clerk is making a tirade, or angry speech, nor does it make sense to treat one’s entire job like a tirade.

Casual nonchalance, farce.