Sides with Henry of Navarre on this spot (4)
I believe the answer is:
here
'on this spot' is the definition.
(I've seen this before)
'sides with henry of navarre' is the wordplay.
I cannot quite understand how this works, but
'henry' could be 'h' (symbol for the unit of electrical inductance) and 'h' is present in the answer.
The remaining letters 'ere' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for here that I've seen before include ""___ be dragons" (old map inscription?)" , "Present - at this point" , "final clue?" , "On this spot" , "Present; I say!" .)