Twbydy-am-by-3 -

But the simplest interpretation: = two-by-two = 4; "am" = AM; "by 3" = next to 3 → "4AM beside 3" → puzzle answer "TRI" (three) as the piece.

Alternatively: the answer might be (Roman 3) as the "piece". twbydy-am-by-3

(Roman numeral for 3, "piece" as in a piece of a set). But the simplest interpretation: = two-by-two = 4;

Given the ambiguous nature, I think this is a cryptic instruction: is an anagram of "two by dy" = two by dy? dy = dysprosium. No. "am" = AM

The string appears to be a cryptic clue in the style of a cryptic crossword.

But without more context, the cleanest match to a 3-letter "piece" is (as in a piece of something) — but the wordplay "twbydy" doesn't yield that.