Cap on the old man in American city (5)
I believe the answer is:
Here is my best explanation:
'american city' is the definition.
(I've seen this before)
'cap on the old man' is the wordplay.
'cap' becomes 'tam' (tam is a kind of cap).
'on' means one lot of letters go next to another.
'the old man' becomes 'pa' (both can mean father).
'in' acts as a link.
(Other definitions for tampa that I've seen before include "Port of western Florida", "Florida resort", "American resort", "US town", "US resort", "stateside destination", "City in Florida", "American city", "US city" and "Floridian resort".)