Met up with annoying person causing storm (7)
I believe the answer is:
tempest
'storm' is the definition.
(tempest is a kind of storm)
'met up with annoying person' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'with' means one lot of letters go next to another.
'annoying person' becomes 'pest' (I've seen this before).
'met' back-to-front is 'tem'.
'tem'+'pest'='TEMPEST'
'causing' acts as a link.
(Other definitions for tempest that I've seen before include "commotion" , "Cyclone" , "terrible blow" , "A violent storm like Shakespeare's" , "violent uproar" .)