Realise I've developed stabbing pain (7)
I believe the answer is:
achieve
'realise' is the definition.
(I've seen this in another clue)
'i've developed stabbing pain' is the wordplay.
'developed' is an anagram indicator.
'stabbing' is an insertion indicator (some letters stab themselves into others).
'pain' becomes 'ache' (ache is a kind of pain).
'ive' is an anagram of 'iev'.
'iev' inserted inside 'ache' is 'ACHIEVE'.
(Other definitions for achieve that I've seen before include "wrap up" , "Perform" , "Have ice (anag.)" , "Consummate" , "Bring to a successful outcome" .)