Stroke is worried before onset of squall (6)
I believe the answer is:
caress
'stroke' is the definition.
(synonyms)
'is worried before onset of squall' is the wordplay.
'is worried' becomes 'cares' (to care is show concern or worry).
'before' is a charade indicator (letters next to each other).
'onset of' indicates taking the first letters.
The initial letter of 'squall' is 's'.
'cares'+'s'='CARESS'
(Other definitions for caress that I've seen before include "Stoke affectionately" , "Gentle stroke" , "Scares into handle lovingly" , "Scares with loving gesture" , "Gentle loving touch" .)