Son and husband boarding reserved coach (6)
I believe the answer is:
school
'coach' is the definition.
(both can mean to teach or train)
'son and husband boarding reserved' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'and' says to put letters next to each other.
'husband' becomes 'h' (abbreviation).
'boarding' is an insertion indicator.
'reserved' becomes 'cool' (similar in meaning).
'h' put into 'cool' is 'chool'.
's'+'chool'='SCHOOL'
(Other definitions for school that I've seen before include "group of swimmers" , "Train (of thought?)" , "Educational facility" , "Educate; group" , "See 7" .)