Having unpleasant personal problem on location has no effect (7)
I believe the answer is:
placebo
'no effect' is the definition.
'placebo' can be an answer for 'effect' (I have seen 'An effect' mean 'placebo' so perhaps 'effect' could also mean 'placebo'). I'm not certain of the 'no' bit.
'having unpleasant personal problem on location' is the wordplay.
I cannot really understand how this works, but
'location' could be 'place' (a location is a place) and 'place' is located in the answer.
'personal problem' could be 'bo' (informal abbreviation for body odour) and 'bo' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'has' acts as a link.
Can you help me to learn more?
(Other definitions for placebo that I've seen before include "Medicine that's not" , "Medicine having no physiological effect" , "Measure purely to calm or humour another" , "innocuous dose" , "Medicament often given as a pacifier" .)