And volcanic mountain rises moderately slowly (7)
I believe the answer is:
andante
'moderately slowly' is the definition.
(I've seen this before)
'and volcanic mountain rises' is the wordplay.
'volcanic mountain' becomes 'etna' (I've seen this in another clue).
'rises' says the letters should be written in reverse.
'etna' backwards is 'ante'.
'and'+'ante'='ANDANTE'
(Other definitions for andante that I've seen before include "tad slow for 9 [FLAUTIST] ?" , "Musically, in moderately slow time" , "Fairly slow (mus.)" , "Unhurried pace" , "at a gentle pace" .)