Hi, orientfan.
28a – Ivor the Engine was a childrens’ TV programme (apparently originally broadcast in 1958 but revived in 1975). The wordplay gives LIVOR for “black and blue”, minus the first letter, so ending up with IVOR.
21d – I think that “males on the run” leads to ROISTERS, “sacking one” implies that the I is omitted, leaving ROSTERS, which is defined by “duty allocations”. The word “impresario” is an extra word that must be omitted. I hadn’t realised that “roister” can be a noun, defined in Chambers as “a blusterer; a noisy reveller”. I must say that I’m not entirely convinced by this clue, as I can’t find a clear definition of “run” that fits the definition (either as a noun or as a verb) of “roister”, so I might not have this right. Also, I can’t see a role for the word “over” in the clue after the extra word is deleted, so there may be a better parsing for this clue.
And, escuan, you can choose
either the first or the last letter of each of the extra words to make the common phrase, with the other letter of each word giving the anagram. In 8d, I saw “etching” as indicating that something indicated by “line” was included in something indicated by “stone”.