keep back

keep back (third-person singular simple present keeps back, present participle keeping back, simple past and past participle kept back)

1. (transitive) To hold back; to refuse to give or share.
2. (transitive) To restrict or restrain.
   • 2017 November 10, Daniel Taylor, “Youthful England earn draw with Germany but Lingard rues late miss”, in The Guardian (London)‎:

     Germany eased off in the second half and this was a night when Joachim Löw, like Southgate, took the opportunity to keep back his best XI.

3. (transitive) To prevent (a pupil) from advancing in a course.