Virgin Trains' pie not a crumble (8)
I believe the answer is:
Here is my best explanation:
'virgin' is the definition.
'trains' pie not a crumble' is the subsidiary indication.
'not' indicates named letters should be taken away.
'crumble' indicates an anagram.
'trainspie' with 'a' taken out is 'trinspie'.
'trinspie' with letters rearranged gives 'pristine'.
(Other definitions for pristine that I've seen before include "Pint, sire? (anag)", "Unchanged or unspoilt", "Spotless", "Unspoilt", "Fresh and clean as if new", "Pure - tire spin (anag)", "Immaculate", "Original, unspoiled", "Like new" and "Immaculately clean, unused or untouched".)