Hope for power in cult (8)
I believe the answer is:
prospect
'hope' is the definition.
(thesaurus)
'for power in cult' is the wordplay.
'for' becomes 'pro' (as in being 'pro' something).
'power' becomes 'p' (symbol in physics).
'in' means one lot of letters goes inside another.
'cult' becomes 'sect' (religious sect).
'p' put into 'sect' is 'spect'.
'pro'+'spect'='PROSPECT'
(Other definitions for prospect that I've seen before include "Outlook or panorama" , "Explore in search of something, perhaps gold" , "Chance of success" , "Likely candidate" , "likelihood of event taking place" .)