Ray and Old Bob - parasites employed by a sole distributor? (4,5)

'a sole distributor?' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?

'ray and old bob parasites employed by' is the wordplay.
'ray' becomes 'fish' (I can't justify this - if you can you should believe this answer much more).
'and' means one lot of letters go next to another.
'old bob' becomes 's' (abbreviation for bob or shilling used before f97f).
'parasites' becomes 'lice' (lice are parasitic insects).
'employed by' is a charade indicator (letters next to each other).
'fish'+'s'+'lice'='FISH-SLICE'

Can you help me to learn more?