Intensify the colour of the globe – an unusual blue (8)
I believe the answer is:
redouble
'intensify' is the definition.
(redoubling is a kind of intensifying)
'the colour of the globe an unusual blue' is the wordplay.
'the colour of the globe' becomes 'redo' (I can't explain this - if you can you should give a lot more credence to this answer).
'an unusual' indicates anagramming the letters.
'blue' with letters rearranged gives 'uble'.
'redo'+'uble'='REDOUBLE'
Can you help me to learn more?
(Other definitions for redouble that I've seen before include "Be louder to multiply by four - say degree of effort" , "Bridge call" , "Produce more" , "increase fourfold" , "Bid" .)