In favour of second CIA operation being dull (7)
I believe the answer is:
prosaic
'being dull' is the definition.
(similar in meaning)
'in favour of second cia' is the wordplay.
'in favour' becomes 'pro' (I've seen this before).
'of' is an anagram indicator (the answer comes from or 'of' the letters).
'second' becomes 's' (common abbreviation).
's'+'cia'='scia'
'scia' is an anagram of 'saic'.
'pro'+'saic'='PROSAIC'
'operation' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for prosaic that I've seen before include "boring!" , "Pedestrian, unimaginative" , "routine" , "Lacking originality" , "Lacking wit or imagination, dull" .)