Used to test broken gauge with single pin (9)

I believe the answer is:

guineapig

I'm a little stuck... Click here to teach me more about this clue!

'used to test' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'broken gauge with single pin' is the wordplay.
'broken' is an anagram indicator.
'with' means one lot of letters go next to another.
'single' becomes 'I' (one).
'i'+'pin'='ipin'
'gauge' after 'ipin' is 'ipingauge'.
'ipingauge' is an anagram of 'GUINEAPIG'.

Can you help me to learn more?

(Another definition for guineapig that I've seen is " One experimented with".)

I've seen this clue in The Irish Times.

Want a hint initially instead of a full solution? Install my app