Tried out an oddly regressive inspection (5)
I believe the answer is:
audit
'inspection' is the definition.
(I've seen this before)
'tried out an oddly regressive' is the wordplay.
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
'regressive' says the letters should be written backwards (to regress is to go backwards).
'tried'+'out'+'an'='triedoutan'
The alternate letters of 'triedoutan' are 'tidua'.
'tidua' written backwards gives 'AUDIT'.
(Other definitions for audit that I've seen before include "Investigate" , "Roman Aquae Sulis" , "vetting of books" , "Carry out annual check of firm's accounts" , "assessment" .)