respectfully; discreet
謹賀新年（きんがしんねん）
Happy New Year (formal)
On-reading (キン) is used in compounds; kun-reading (つつし(む)) is used standalone or with okurigana. This kanji forms verbs/adjectives with okurigana. Practice both the word form and compound forms.
From the JLP Quiz question bank — the word in the form it is actually tested in.
「謹慎」の読み方はどれか。
Answer: きんしん
書面___ご報告申し上げます。
Answer: をもって
