Activities advisor centrally books online holidays (9)
I believe the answer is:
interests
'activities' is the definition.
(interest is a kind of activity)
'advisor centrally books online holidays' is the wordplay.
'centrally' indicates the central letters.
'books' becomes 'NT' (abbreviation for New Testament).
'online' becomes 'e' (as in e-mail or e-commerce).
'holidays' becomes 'rests' (I've seen this before).
The centre of 'advisor' is 'i'.
'i'+'nt'+'e'+'rests'='INTERESTS'
(Other definitions for interests that I've seen before include "Holds the attention" , "Activities or subjects which one enjoys" , "Pastimes or concerns" , "is fascinating" , "Pursuits of triteness" .)