Jet fellow mentioned (6)
I believe the answer is:
geyser
'jet' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for geyser that I've seen before include "upsurge" , "wall heater" , "A spring sending up columns of hot water" , "Spring that discharges steam and hot water" , "spouter!" .)