Teach the others about self-control (9)
I believe the answer is:
restraint
'self-control' is the definition.
(I've seen this before)
'teach the others about' is the wordplay.
'teach' becomes 'train' (training is a kind of teaching).
'the others' becomes 'rest' (eg the rest of a group).
'about' is an insertion indicator.
'train' placed inside 'rest' is 'RESTRAINT'.
(Other definitions for restraint that I've seen before include "Self-control" , "Self-discipline" , "Start rain as an impediment" , "Curb" , "Something that holds back" .)