A pop star has to shake and moan (7)
I believe the answer is:
madonna
'a pop star' is the definition.
(I've seen this before)
'shake and moan' is the wordplay.
'shake' indicates an anagram.
'and'+'moan'='andmoan'
'andmoan' is an anagram of 'MADONNA'.
'has to' acts as a link.
(Other definitions for madonna that I've seen before include "Picture or statue of the Virgin Mary" , "Religious work" , "US female singer" , "Virgin Mary; singer" , "Lady - type of 1 across" .)