Teach the others to hold in, or curb (9)
I believe the answer is:
restraint
'curb' is the definition.
(I've seen this in another clue)
'teach the others to hold' is the wordplay.
'teach' becomes 'train' (training is a kind of teaching).
'the others' becomes 'rest' (I've seen this before).
'to hold' indicates putting letters inside.
'train' put into 'rest' is 'RESTRAINT'.
'in or' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for restraint that I've seen before include "Self-discipline" , "Limiting device" , "Restriction, limit" , "Reserve" , "controlling influence" .)