Normal clue lacking definition ultimately becomes elementary? (9)
I believe the answer is:
Here is my best explanation:
'elementary?' is the definition.
'normal clue lacking definition ultimately' is the subsidiary indication.
I cannot quite see how this works, but
an anagram of 'clue' is 'lecu' which is present in the answer.
The remaining letters 'molar' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'becomes' is the link.
(Other definitions for molecular that I've seen before include "Relating to groups of atoms bonded together", "Relating to the smallest particles of a substance" and "Dealing with small particles".)