Irreverent icon having change of heart (7)
I believe the answer is:
godless
'irreverent' is the definition.
(I know that irreverent can be written as godless)
'change of heart' is the wordplay.
'change' becomes 'go' (going is a kind of changing).
'of heart' becomes 'dless' (I can't explain this - if you can you should give a lot more credence to this answer).
'go'+'dless'='GODLESS'
'icon having' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for godless that I've seen before include "Of no faith" , "Wicked - impious" , "Irreverent - atheistic" , "Heathen" , "Profane, wicked" .)