Craft invading deserted eighth planet (5)
I believe the answer is:
earth
'planet' is the definition.
(Earth is an example)
'craft invading deserted eighth' is the wordplay.
'craft' becomes 'art' (both can mean cunning or trickery).
'invading' indicates putting letters inside.
'deserted' says to hollow out the word (remove centre letters) (middle letters must vacate or desert the word).
'eighth' with its middle taken out is 'eh'.
'art' going within 'eh' is 'EARTH'.
(Other definitions for earth that I've seen before include "Fox's underground lair" , "Fox's burrow" , "hideaway" , "Terra firma" , "Fox's or badger's lair" .)