Worried RAF leaders for instance make fighters stand by (6)
I believe the answer is:
affirm
'fighters stand by' is the definition.
I can't judge whether this definition defines the answer.
'worried raf leaders for instance make' is the wordplay.
'worried' is an anagram indicator (worry can mean to interfere with or disturb).
'leaders' suggests taking the first letters.
The initial letters of 'for instance make' is 'fim'.
'raf'+'fim'='raffim'
'raffim' is an anagram of 'AFFIRM'.
Can you help me to learn more?
(Other definitions for affirm that I've seen before include "Make a formal declaration (rather than an oath)" , "Declare one's commitment (to)" , "Publicly state" , "State as a fact, assert" , "Substantiate" .)