Potentially lousy sex with Trump, initially, in his home city (5)
I believe the answer is:
nitty
'potentially lousy' is the definition.
'nitty' can be an answer for 'lousy' (I've seen this before). I'm unsure of the 'potentially' bit.
'sex with trump initially in his home city' is the wordplay.
I cannot really see how this works, but
'sex' could be 'it' (common euphemism) and 'it' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for nitty that I've seen before include "Gritty's partner?" , "lousy" , "___-gritty, the basics" .)