Collocations for clientele - noun

large, narrow, small
broad, diverse
loyal
regular, usual
exclusive, fashionable, select, upscale (AmE)
international

attract, have
The restaurant has a large regular clientele.

cater for, cater to, serve
The boutique caters for a rather select clientele.

build (esp. AmE), build up (esp. BrE), develop, establish
It takes time to build (up) a clientele.