A gel NASA developed includes iodine for pain relief (9)
I believe the answer is:
analgesia
'for pain relief' is the definition.
(I've seen this before)
'a gel nasa developed includes iodine' is the wordplay.
'developed' is an anagram indicator.
'includes' means one lot of letters goes inside another.
'iodine' becomes 'I' (chemical symbol).
'a'+'gel'+'nasa'='agelnasa'
'agelnasa' anagrammed gives 'analgesa'.
'analgesa' placed around 'i' is 'ANALGESIA'.
(Other definitions for analgesia that I've seen before include "result of medication?" , "As a linage (anag) - insensibility to pain" , "Inability to feel pain" , "Loss of pain" , "No hard feelings" .)