Rely almost entirely on a new church for sympathetic response (9)
I believe the answer is:
resonance
'sympathetic response' is the definition.
The answer and definition can be both types of natural phenomena as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'rely almost entirely on a new church' is the wordplay.
'rely' becomes 'rest' (rely can mean to rest or depend on).
'almost entirely' means to remove the last letter (most but not all of the word).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'church' becomes 'ce' (Church of England).
'rest' with its last letter removed is 'res'.
'res'+'on'+'a'+'n'+'ce'='RESONANCE'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for resonance that I've seen before include "shaking" , "Sympathetic vibration" , "Vibrancy" , "Deep, clear, ringing quality" , "continuation of noise" .)