Relative having a cheerful manner without any frills (4)
I believe the answer is:
aunt
'relative' is the definition.
(aunt is a kind of relative)
'having a cheerful manner without any frills' is the wordplay.
'having a cheerful manner' becomes 'jaunty' (jaunty means cheerful or lively).
'without any frills' says to take the centre (the edges or \'frills\' of the word are removed).
The middle letters of 'jaunty' are 'AUNT'.
(Other definitions for aunt that I've seen before include "Tuna gone bad for the relative" , "Female relation" , "Sister of father/mother" , "Wife of one's uncle" , "Charley's in play?" .)