Worry when sibling loses his second (6)
I believe the answer is:
bother
'worry' is the definition.
(I've seen this before)
'sibling loses his second' is the wordplay.
I cannot quite understand how this works, but
'second' could be 'other' (I've seen this before) and 'other' is present in the answer.
A single letter 'b' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'when' is the link.
Can you help me to learn more?
(Other definitions for bother that I've seen before include "Worry, disturb" , "Fuss; oh no!" , "Fuss and nuisance" , "Badger" , "Fuss and irritant" .)