Stick together in the alternating current near the island (7)
I believe the answer is:
accrete
'stick together' is the definition.
Although both the answer and definition are verbs in their base form, I can't see how they can define each other.
'alternating current near the island' is the wordplay.
'alternating current' becomes 'AC' (synonyms).
'near the' means one lot of letters go next to another.
'island' becomes 'Crete' (Greek island).
'ac'+'crete'='ACCRETE'
'in the' acts as a link.
Can you help me to learn more?
(Other definitions for accrete that I've seen before include "Grow together, unite" , "Become attached" , "get together" , "Build up" , "Form by coalescence" .)