Growth of rock, with wind instrument if something in vogue (9)
I believe the answer is:
saxifrage
'something in vogue' is the definition.
I can't judge whether this defines the answer.
'growth of rock with wind instrument if' is the wordplay.
'growth of rock' becomes 'rage' (I can't explain this - if you can you should give a lot more credence to this answer).
'with' says to put letters next to each other.
'wind instrument' becomes 'sax' (sax is a kind of wind instrument).
'sax'+'if'='saxif'
'rage' put after 'saxif' is 'SAXIFRAGE'.
Can you help me to learn more?
(Other definitions for saxifrage that I've seen before include "flower" , "Plant such as London pride" , "alpine plant" , "Low-growing plant" .)