Got lather worked up somewhat slowly (9)
I believe the answer is:
larghetto
'slowly' is the definition.
(I've seen this before)
'got lather worked up' is the wordplay.
'worked up' indicates anagramming the letters.
'got'+'lather'='gotlather'
'gotlather' is an anagram of 'LARGHETTO'.
'somewhat' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for larghetto that I've seen before include "rather slowly" , "Slowish" , "In a fairly slow tempo (>music)" , "Rather slow" , "Somewhat slow (music)" .)