Explain delicate manoeuvring about uniform (9)
I believe the answer is:
Here is my best explanation:
'explain' is the definition.
(elucidating is a kind of explaining)
'delicate manoeuvring about uniform' is the subsidiary indication.
'manoeuvring' indicates anagramming the letters.
'about' indicates putting letters inside.
'uniform' becomes 'u' (phonetic alphabet: alpha, bravo, charlie etc.).
'delicate' anagrammed gives 'elcidate'.
'elcidate' placed around 'u' is 'elucidate'.
(Other definitions for elucidate that I've seen before include "Shed light on, clarify", "Explain", "Make clear, explain", "Throw light on a problem, make clear (9)", "Shed light upon" and "Make clear and more comprehensible".)