Relative regularly appearing in bikini contest's magazine (7)
I believe the answer is:
kinsman
'relative' is the definition.
(kinsman is a kind of relative)
'regularly appearing in bikini contest's magazine' is the wordplay.
I cannot quite see how this works, but
'in' is found in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for kinsman that I've seen before include "Blood relative" , "Male relation" , "A blood relation" , "(Male) relative" , "Family member" .)