Caller upset by a line getting signal to proceed (3-5)
I believe the answer is:
all clear
'signal to proceed' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'caller upset by a line' is the wordplay.
'upset' indicates an anagram.
'by' means one lot of letters go next to another.
'line' becomes 'l' (used when specifying particular lines from a poem).
'caller' anagrammed gives 'lclear'.
'a'+'l'='al'
'lclear' after 'al' is 'ALL-CLEAR'.
'getting' acts as a link.
Can you help me to learn more?
(Other definitions for all clear that I've seen before include "Message confirming safety" , "Signal to resume normal activities" , "with absolutely no ambiguity" , "Siren sound to signal end of air raid" , "ARP signal" .)