Train toilet hacks regularly used on return journey (6)
I believe the answer is:
school
'train toilet' is the definition.
'school' can be an answer for 'train' (thesaurus). I am unsure of the 'toilet' bit.
'hacks regularly used on return journey' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'used' indicates anagramming the letters.
'on return' shows that the letters should be reversed in order.
'journey' becomes 'loo' (I can't explain this - if you can you should believe this answer much more).
The alternate letters of 'hacks' are 'hcs'.
'loo' in reverse letter order is 'ool'.
'hcs' is an anagram of 'sch'.
'sch'+'ool'='SCHOOL'
Can you help me to learn more?
(Other definitions for school that I've seen before include "Group of pupils, fish" , "Academy; group of fish" , "A number of swimmers joined" , "Where 2 takes place" , "classes?" .)