It may be cultivated for example in a rum cocktail (8)
I believe the answer is:
geranium
'it may be cultivated' is the definition.
The definition suggests a singular noun which matches the answer.
'example in a rum cocktail' is the wordplay.
'example' becomes 'ge' (I can't justify this - if you can you should believe this answer much more).
'cocktail' indicates an anagram.
'in'+'a'+'rum'='inarum'
'inarum' is an anagram of 'ranium'.
'ge'+'ranium'='GERANIUM'
'for' is the link.
Can you help me to learn more?
(Other definitions for geranium that I've seen before include "Popular flowering pot plant" , "Cultivated pelargonium" , "I run game to get colourful flower for windowbox" , "Flower for a strange Maine rug" , "Cultivated cranesbill" .)