Crossword clue: a measuring instrument for measuring and indicating a quantity such as the thickness of wire or the amount of rain etc.

The most common answer is gage (4 letters).

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

Possible answers

gage 4 letters wn-def

a measuring instrument for measuring and indicating a quantity such as the thickness of wire or the amount of rain etc.

gauge 5 letters wn-def

judge tentatively or form an estimate of (quantities or time)