Clue: Exciting era in which submariner happened on way to measure current (10)
Answer: ANEMOMETER
Explanation: Exciting era in which submariner happened on way to measure current (10)
NEMO ("submariner") + MET ("happened on") in *(era) 
*Captain Nemo was a submariner in some of Jules Vernes's adventure stories, most notably in *20,000 Leagues Under the Sea.