Struggled in San Diego (8)

I believe the answer is:

agonised

I'm a little stuck... Click here to teach me more about this clue!

'struggled' is the definition.
(I've seen this before)

'san diego' is the wordplay.
'san diego' anagrams to 'AGONISED'.
Though, I'm not sure how the anagram is indicated.

'in' acts as a link.

Can you help me to learn more?

(Other definitions for agonised that I've seen before include "worried a lot" , "Diagnose (anag)" , "Very pained" , "Dog in sea (anag) - suffered anguish" , "Suffered mentally in San Diego" .)

I've seen this clue in The Irish Independent.

Want a hint initially instead of a full solution? Install my app