Took a seat outside. Weather first hit hard (4)
I believe the answer is:
swat
'hit hard' is the definition.
(I've seen this in another clue)
'took a seat outside weather first' is the wordplay.
'took a seat' becomes 'sat' (I've seen this in another clue).
'outside' is an insertion indicator (some letters go outside others).
'weather first' becomes 'w' (1st letter of 'weather').
'sat' enclosing 'w' is 'SWAT'.
(Other definitions for swat that I've seen before include "Hit hard, say fly, with something flat" , "land crushing blow" , "Hit and crush (a fly)" , "Hit smartly" , "Strike sharply (at fly?)" .)