Romeo donning short wig starts to ridicule senior actors (8)
I believe the answer is:
troupers
'actors' is the definition.
(trouper is a kind of actor)
'romeo donning short wig starts' is the wordplay.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'donning' indicates putting letters inside (I've seen this in other clues).
'short' means to remove the last letter.
'wig' becomes 'toupee' (I've seen this before).
'starts' becomes 'rs' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'toupee' with its last letter removed is 'toupe'.
'r' placed into 'toupe' is 'troupe'.
'troupe'+'rs'='TROUPERS'
'to ridicule senior' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
(Another definition for troupers that I've seen is " Old actors".)