Cocks perhaps on English church disappear (8)
I believe the answer is:
evanesce
'disappear' is the definition.
(I know that evanesce is a more specific form of the action disappear)
'cocks perhaps on english church' is the wordplay.
'cocks perhaps' becomes 'vanes' (I can't justify this - if you can you should give a lot more credence to this answer).
'on' says to put letters next to each other.
'english' becomes 'E' (abbreviation).
'church' becomes 'CE' (Church of England).
'vanes' after 'e' is 'evanes'.
'evanes'+'ce'='EVANESCE'
Can you help me to learn more?
(Other definitions for evanesce that I've seen before include "Fade away" , "Seen cave (anag) -- disappear gradually" , "Fade quickly from sight" , "Shimmering" .)