Call them regularly and help out United (9)
I believe the answer is:
telephone
'call' is the definition.
(synonyms)
'them regularly and help out united' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'and' is a charade indicator (letters next to each other).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'united' becomes 'one' (as in a phrase like 'we are one').
The alternating letters of 'them' are 'te'.
'help' is an anagram of 'leph'.
'te'+'leph'+'one'='TELEPHONE'
(Other definitions for telephone that I've seen before include "Mobile, for instance" , "Call, ring" , "communicator" , "Worldwide system of communication" , "Communicating tool" .)