After month in retreat, a glimpse of Ronnie Wood (5)
I believe the answer is:
cedar
'wood' is the definition.
(I know that cedar is a type of wood)
'after month in retreat a glimpse of ronnie' is the wordplay.
'after' means one lot of letters go next to another.
'month' becomes 'dec' (abbreviation for December).
'in retreat' says the letters should be written in reverse.
'a glimpse of ronnie' becomes 'ar' (I can't explain this - if you can you should give a lot more credence to this answer).
'dec' reversed gives 'ced'.
'ced'+'ar' is 'CEDAR'.
Can you help me to learn more?
(Other definitions for cedar that I've seen before include "Tall conifer" , "may have needles?" , "Fragrant conifer" , "Tree giving fragrant wood" , "Evergreen tree" .)