Relatively anxious to be more incisive (6)
I believe the answer is:
'more incisive' is the definition.
('keen' can be a synonym of 'incisive')
'relatively anxious' is the wordplay.
I cannot really see how this works, but
'anxious' could be 'keen' (I've seen this before) and 'keen' is found within the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'to be' acts as a link.
Can you help me to learn more?
(Other definitions for keener that I've seen before include "more piercing" , "More enthusiastic; wailing mourner" , "More devoted" , "one who lives by wailing?" , "person mourning" .)