Teacher first and last, holding out for revision (5)
I believe the answer is:
tutor
'teacher' is the definition.
(tutor is a kind of teacher)
'first and last holding out for revision' is the wordplay.
'first and last' becomes 'tr' (I am not sure about this - if you are sure you should believe this answer much more).
'holding' is an insertion indicator.
'for revision' is an anagram indicator (I've seen this in other clues).
'out' is an anagram of 'uto'.
'tr' going around 'uto' is 'TUTOR'.
Can you help me to learn more?
(Other definitions for tutor that I've seen before include "Guardian" , "Coach, teacher" , "Trout (anag)" , "Individual teacher" , "Private educator" .)