Determined learner dons felt sorry for (5)
I believe the answer is:
ruled
'determined' is the definition.
(ruling is a kind of determining)
'learner dons felt sorry for' is the wordplay.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'dons' is an insertion indicator (don means to wear or put on).
'felt sorry for' becomes 'rued' (I've seen this in another clue).
'l' going into 'rued' is 'RULED'.
(Other definitions for ruled that I've seen before include "Governed or commanded" , "Exercised control over" , "Made authoritative statement" , "Reigned or ordered" , "Held the reins" .)