First officer who looks after himself, primarily? (6,3)
I believe the answer is:
number one
'first' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for number one that I've seen before include "Cut" , "Informally and numerically, oneself" , "Top-of-the-charts hit" , "leader" , "top-selling record" .)