Branch of learning — I have to be expressing personal ideas (10)

I believe the answer is:

subjective

'be expressing personal ideas' is the definition.
(as in a subjective opinion)

'branch of learning i have' is the wordplay.
'branch of learning' becomes 'subject' (eg an academic subject).
'i have' becomes 'I've' (contraction of 'I have').
'subject'+'ive'='SUBJECTIVE'

'to' is the link.

(Another definition for subjective that I've seen is " judged personally".)

I've seen this clue in The Guardian.

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