Fruit round mountains (7)
I believe the answer is:
oranges
'fruit' is the definition.
(oranges are a type of fruit)
'round mountains' is the wordplay.
'round' becomes 'o' (round can mean a round object).
'mountains' becomes 'ranges' (mountain ranges).
'o'+'ranges'='ORANGES'
(Other definitions for oranges that I've seen before include "Go snare these fruits" , "a zesty lot" , "They are not the only fruit, wrote Jeanette Winterson" , "Navel, blood and Seville are all varieties of these" , "Citrus fruit" .)