Follow trial’s development (5)
I believe the answer is:
trail
'follow' is the definition.
(trail can mean to follow in secret)
'trial's development' is the wordplay.
'development' indicates an anagram.
'trial' is an anagram of 'TRAIL'.
(Other definitions for trail that I've seen before include "Drag behind" , "Rough track blazed through wild or hilly country" , "Beaten path; lag" , "Track - be behind" , "Mark left where something has passed - follow it" .)