It took a month for us to name this god! (5)
I believe the answer is:
janus
'it took a month for us to name this god' is the definition.
'Janus' can be an answer for 'god' (Roman god). I'm not sure about the rest of the definition.
'us to name this god' is the wordplay.
I cannot quite see how this works, but
'us' is found in the answer.
'name' could be 'jan' and 'jan' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for janus that I've seen before include "Roman god of doors, usually two-faced - a month is named for him" , "Two-faced Roman god who guarded doors and gates" , "Two-faced deity" , "Roman deity who faces front and back" , "Roman god of doors and beginnings" .)