At uni, Jack pens work of an acceptable standard (2,2,3)
I believe the answer is:
up to par
'of an acceptable standard' is the definition.
'at uni jack pens work' is the wordplay.
'at uni' becomes 'up'.
'jack' becomes 'tar' (I've seen this before).
'pens' indicates putting letters inside.
'work' becomes 'op' (abbreviation for opus).
'tar' enclosing 'op' is 'topar'.
'up'+'topar'='UP TO PAR'
(Other definitions for up to par that I've seen before include "Of good enough quality" , "Performing well" .)