Customers of guides with no hearts (5)
I believe the answer is:
users
'customers' is the definition.
(users of a service or product)
'guides with no hearts' is the wordplay.
'guides' becomes 'ushers' (ushering is a kind of guiding).
'with no' suggests deleting specific letters.
'hearts' becomes 'h' (abbreviation used in card games e.g. bridge).
'ushers' with 'h' taken away is 'USERS'.
'of' acts as a link.
(Other definitions for users that I've seen before include "Ruses for employers" , "They employ" , "subscribers" , "Utilisers" , "People with a drug habit" .)