Disregard groin injury initially excruciating (6)
I believe the answer is:
ignore
'disregard' is the definition.
('ignore' can be a synonym of 'disregard')
'groin injury initially excruciating' is the wordplay.
'injury' is an anagram indicator.
'initially' indicates taking the first letters.
The first letter of 'excruciating' is 'e'.
'groin' anagrammed gives 'ignor'.
'ignor'+'e'='IGNORE'
(Other definitions for ignore that I've seen before include "Discount" , "Region in which to snub" , "Walk away from" , "set aside" , "Fail to notice (6)" .)