Turns up, no teacher has heads probably messing indoors put in detention (8)
I believe the answer is:
imprison
'put in detention' is the definition.
(I've seen this before)
'turns up no teacher has heads probably messing indoors' is the wordplay.
'turns up' is a reversal indicator.
'teacher' becomes 'sir' (I've seen this before**).
'has' says to put letters next to each other.
'heads' indicates taking the first letters.
The initial letters of 'probably messing indoors' is 'pmi'.
'no'+'sir'+'pmi'='nosirpmi'
'nosirpmi' backwards is 'IMPRISON'.
(Other definitions for imprison that I've seen before include "Put away" , "Lock up" , "Confine" , "Put behind bars" , "Bang up" .)