Toenail regularly selected for greenish colour (4)
I believe the answer is:
teal
'greenish colour' is the definition.
'teal' can be an answer for 'colour' (teal is a kind of colour). I'm not certain of the 'greenish' bit.
'toenail regularly selected' is the wordplay.
'regularly selected' means one should take alternating letters (letters taken at regular intervals).
The alternate letters of 'toenail' are 'TEAL'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for teal that I've seen before include "Type of duck" , "Strange tale of a duck" , "Raise (subject matter)" , "Dark green-blue; duck" , "Small, short-necked duck" .)