Rotarian and two daughters rambling and slowing down (10)
I believe the answer is:
ritardando
'slowing down' is the definition.
(I've seen this before)
'rotarian and two daughters rambling' is the wordplay.
'two daughters' means two substitutions for 'daughters'.
'and' means one lot of letters go next to another.
'daughters' becomes 'd' (genealogical abbreviation for daughters).
'daughters' becomes 'd' (genealogical abbreviation for daughters).
'rambling' indicates an anagram.
'd'+'d'='dd'
'rotarian' after 'dd' is 'ddrotarian'.
'ddrotarian' anagrammed gives 'RITARDANDO'.
'and' is the link.
(Another definition for ritardando that I've seen is " slowing down".)