Put up across street for experiments (5)
I believe the answer is:
tests
'experiments' is the definition.
(test is a kind of experiment)
'put up across street' is the wordplay.
'put' becomes 'set' (setting is a kind of putting).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'across' is an insertion indicator.
'street' becomes 'st'.
'set' in reverse letter order is 'tes'.
'tes' placed around 'st' is 'TESTS'.
'for' is the link.
(Other definitions for tests that I've seen before include "Examinations, trials" , "Trials for cricketers" , "Puts to proof at cricket matches" , "International cricket matches" , "Critically examines" .)