Painter of geologer oddly missed out green (2,5)
I believe the answer is:
el greco
'painter' is the definition.
(nickname of Domenikos Theotokpoulos, 1541-1641)
'geologer oddly missed out green' is the wordplay.
'oddly missed out' means one should take alternating letters (letters in odd-numbered positions removed).
'green' becomes 'eco' (abbreviation for ecological).
The alternating letters of 'geologer' are 'elgr'.
'elgr'+'eco'='EL GRECO'
'of' is the link.
(Other definitions for el greco that I've seen before include "Spanish painter born in Greece" , "Sp. painter, born Domen- ikos Theotokopoulos" , "Greek born Spanish painter" , "Domenikos Theotokopoulos" , "Spanish painter, nicknamed for his place of birth" .)