Run true to form in training (7)
I believe the answer is:
nurture
'training' is the definition.
(thesaurus)
'run true to form' is the wordplay.
'to form' indicates anagramming the letters.
'run'+'true'='runtrue'
'runtrue' anagrammed gives 'NURTURE'.
'in' is the link.
(Other definitions for nurture that I've seen before include "Encourage development of (a child)" , "Supply sustenance to" , "Foster, feed" , "Care for during upbringing" , "Help develop and grow" .)