Don't allow a GP going off to get a locum (7)
I believe the answer is:
stopgap
'a locum' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'don't allow a gp going off to get' is the wordplay.
'don't allow' becomes 'stop' (I've seen this before).
'going off' indicates an anagram (letters go or move around).
'to get' means one lot of letters goes inside another.
'a'+'gp'='agp'
'agp' is an anagram of 'gap'.
'stop' put into 'gap' is 'STOPGAP'.
Can you help me to learn more?
(Other definitions for stopgap that I've seen before include "caretaker" , "Temporary fix" , "Makeshift" , "Provisional" , "A temporary or impromptu substitute" .)