Uninteresting ladder trial (3,3)
I believe the answer is:
dry run
'trial' is the definition.
(I've seen this before)
'uninteresting ladder' is the wordplay.
'uninteresting' becomes 'dry' (dry can mean dull or boring).
'ladder' becomes 'run' (both can mean a tear in tights).
'dry'+'run'='DRY RUN'
(Other definitions for dry run that I've seen before include "event staged by AA?" , "Practice session, rehearsal" , "Dummy trial on thirsty trot?" , "Rehearsal, test" , "Kind of rehearsal like thirsty trot" .)