One of nine sisters in hospital, many I suspect associated with former college (10)

'one of nine sisters' is the definition.
(one of the nine Muses in Greek myth)

'hospital many i suspect associated with former college' is the wordplay.
'hospital' becomes 'h'.
'suspect' indicates an anagram.
'associated with' says to put letters next to each other.
'former college' becomes 'poly' (polytechnic).
'many'+'i'='manyi'
'manyi' anagrammed gives 'ymnia'.
'h'+'ymnia'='hymnia'
'hymnia' put after 'poly' is 'POLYHYMNIA'.

'in' acts as a link.