Believe singer shelters a second follower (6)
I believe the answer is:
chaser
'follower' is the definition.
(I know that chaser is a type of follower)
'believe singer shelters a second' is the wordplay.
'believe singer' becomes 'cher' (I've seen this in another clue).
'shelters' is an insertion indicator.
'second' becomes 's' (common abbreviation).
'a'+'s'='as'
'cher' going around 'as' is 'CHASER'.
(Other definitions for chaser that I've seen before include "Drink that follows immediately after another one" , "Pursuer - of beer after whiskey?" , "Different kind of drink - horse" , "Hunter; drink" , "Drink following another of a different kind" .)