My true story about an excursion (7,4)
I believe the answer is:
mystery tour
'an excursion' is the definition.
(I have seen 'Suspenseful excursion ' mean 'mystery tour' so perhaps 'excursion' could also mean 'mystery tour')
'my true story about' is the wordplay.
'about' is an anagram indicator.
'true'+'story'='truestory'
'truestory' with letters rearranged gives 'sterytour'.
'my'+'sterytour'='MYSTERY TOUR'
(Other definitions for mystery tour that I've seen before include "The Beatles had a magical one" , "Of which the destinations are secret" , "Suspenseful excursion" , "A journey to the unknown" , "Trip to places unknown" .)