Setter's old, funny and latterly ignoring the odds getting extreme admiration (8)
I believe the answer is:
Here is my best explanation:
'extreme admiration' is the definition.
(I've seen this before)
'setter's old funny and latterly ignoring the odds' is the wordplay.
'setter' becomes 'i' (the person that set the crossword).
'funny' indicates an anagram.
'and' means one lot of letters go next to another.
'ignoring the odds' indicates alternate letters (letters in odd-numbered positions are removed).
The alternate letters of 'latterly' are 'atry'.
'old' with letters rearranged gives 'dol'.
'getting' is the link.
(Other definitions for idolatry that I've seen before include "Worship of carved images", "Worship of carved image", "Worship of false gods", "Graven image worship", "Icon worship", "Extreme admiration", "Worshipping", "Adroitly (anag.)", "Getting worked up by image" and "Adulation".)