Site old boy set up, producing psychological medicine (7)
I believe the answer is:
placebo
'psychological medicine' is the definition.
'placebo' can be an answer for 'medicine' (placebo is a kind of medicine). I'm not sure about the 'psychological' bit.
'site old boy set up' is the wordplay.
'site' becomes 'place' (synonyms).
'old boy' becomes 'OB' (abbreviation for a private school 'old boy').
'set up' says the letters should be written in reverse (in a down clue, letters go up).
'ob' reversed gives 'bo'.
'place'+'bo'='PLACEBO'
'producing' is the link.
Can you help me to learn more?
(Other definitions for placebo that I've seen before include "Medicine with no therapeutic effect" , "Medicine having no physiological effect" , "Medicine given for its psychological benefit alone" , "memorial service" , "Medicine with no effect used in drug trials" .)