To make a girl a leader of men is not bright! (3)
I believe the answer is:
dim
'not bright' is the definition.
(I've seen this in another clue)
'to make a girl a leader of men' is the wordplay.
'to make a girl' becomes 'di' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a leader of' suggests taking the first letters.
The initial letter of 'men' is 'm'.
'di'+'m'='DIM'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for dim that I've seen before include "Slow-witted" , "Vague" , "Gloomy; dull" , "Unpromising" , "Faint (light)" .)