Had become tense (10)
I believe the answer is:
pluperfect
This clue might be a double definition.
'had' is the first definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs can occasionally define each other.
'tense' is the second definition.
(the pluperfect is a grammatical tense)
'become' acts as a link.
Can you help me to learn more?
(Other definitions for pluperfect that I've seen before include "Tense with "had" and past participle" , "Verbal tense" , "(In grammar) a tense - per cup left (anag)" .)