One unclued light, defined by the title, is a word that can be divided into three words; each of these defines each of three of the other unclued lights.
 

Across

1    Unsteady in yard, thrust backward (5)
10    Mixture of metals in roof really worked (10, hyphened)
14    Check sun and tide (5)
15    Terms of reference put back (5)
16    Repeated eccentricity suppressed with removal of king (6)
22    Direction to release soft pedal set down in note (8, two words)
23    Denial? One among many concepts (7)
24    Call containing anonymous smear (4)
25    Robust address in hearing (4)
29...