Temp left firm over sign of indecision (5)
I believe the answer is:
locum
'temp' is the definition.
(I have seen 'Professional temp' mean 'locum' so perhaps 'temp' could also mean 'locum')
'left firm over sign of indecision' is the wordplay.
I cannot really see how this works, but
'left' could be 'l' (common abbreviation) and 'l' is located in the answer.
'over' could be 'o' (cricket abbreviation) and 'o' is located in the answer.
The remaining letters 'cum' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for locum that I've seen before include "He fills in" , "Stand-in, for a doctor say" , "Stand-in GP" , "Temporary deputy for doctor" , "Doctor's temporary replacement" .)