Write number appearing within a small range (9)
I believe the answer is:
apennines
'range' is the definition.
(I know that Apennines is a range)
'write number appearing within a small' is the wordplay.
'write' becomes 'pen' (synonyms).
'number appearing' becomes 'nine' (I can't explain this - if you can you should give a lot more credence to this answer).
'within' means one lot of letters goes inside another.
'small' becomes 's' (abbreviation - e.g. clothes size).
'pen'+'nine'='pennine'
'a'+'s'='as'
'pennine' inserted within 'as' is 'APENNINES'.
Can you help me to learn more?
(Other definitions for apennines that I've seen before include "Great mountain range in Italy (9)" , "European range" , "Italian mountains" , "Italian mountain chain" , "Mountain range in central Italy" .)