Trouble when coming to coast (6)
I believe the answer is:
assail
'coast' is the definition.
Although both the answer and definition are verbs in their base form, I don't understand how they can define each other.
'trouble when coming to' is the wordplay.
'trouble' becomes 'ail' (synonyms).
'when' becomes 'ass' (I can't explain this - if you can you should believe this answer much more).
'coming to' says to put letters next to each other.
'ail' put after 'ass' is 'ASSAIL'.
Can you help me to learn more?
(Other definitions for assail that I've seen before include "Charge" , "Molest or harass" , "Attack violently and persistently" , "Make violent attack on" , "Trouble" .)