Experimentation may bring fear across Rhode Island (American state) (5,3,5)
I believe the answer is:
trial and error
'experimentation' is the definition.
(trial and error is a kind of experimentation)
'bring fear across rhode island american state' is the subsidiary indication.
I cannot quite see how this works, but
'bring' could be 'land' (landing is a kind of bringing) and 'land' is present in the answer.
'island' could be 'i' and 'i' is present in the answer.
'american' could be 'a' (common abbreviation - e.g. in organisation names) and 'a' is present in the answer.
'state' could be 'or' and 'or' is present in the answer.
This explanation may well be incorrect...
'may' is the link.
Can you help me to learn more?
(Other definitions for trial and error that I've seen before include "Heuristic process" , "One needs a means of finding the truth" , "Experiment" , "Experimentation through experience" , "Experimenting empirically until a solution is found" .)