Touch of worry with second son (6)
I believe the answer is:
caress
'touch' is the definition.
(I know that caress is a type of stroke)
'worry with second son' is the wordplay.
'worry' becomes 'care' (eg without a care means without a worry).
'with' says to put letters next to each other.
'second' becomes 's' (common abbreviation).
'son' becomes 's' (genealogical abbreviation for son).
'care'+'s'+'s'='CARESS'
'of' is the link.
(Other definitions for caress that I've seen before include "Stroke fondly" , "Embrace with affection" , "Stroke gently" , "Stroke affectionately" , "Tenderly stroke" .)