Scared to help outside RAF order (6)
I believe the answer is:
afraid
'scared' is the definition.
(similar in meaning)
'help outside raf order' is the wordplay.
'help' becomes 'aid' (synonyms).
'outside' is an insertion indicator.
'order' indicates anagramming the letters.
'raf' with letters rearranged gives 'fra'.
'aid' enclosing 'fra' is 'AFRAID'.
'to' is the link.
(Other definitions for afraid that I've seen before include "Nervous" , "Fearful and timid" , "wind up" , "Filled with fear" , "with butterflies" .)