Boy cycles to end of platform to help Southern train attendants (11)

'train attendants' is the definition.
(people in a bride's train or retinue)

'boy cycles to end of platform to help southern' is the wordplay.
I cannot quite see how this works, but
'boy' could be 'des' (short for Desmond) and 'des' is found in the answer.
'help' could be 'aid' (synonyms) and 'aid' is found within the answer.
'southern' could be 's' (abbreviation) and 's' is located in the answer.
The remaining letters 'brim' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).