Pretty girls having twinges after exercising (7)
I believe the answer is:
peaches
'pretty girls' is the definition.
(peach can informally mean an attractive person)
'twinges after exercising' is the wordplay.
'twinges' becomes 'aches'.
'after' says to put letters next to each other.
'exercising' becomes 'pe' (abbreviation for Physical Education).
'aches' after 'pe' is 'PEACHES'.
'having' is the link.
(Other definitions for peaches that I've seen before include "Producing fine specimens" , "Make a speech about the fruit" , "A speech (anag)" , "Juicy fruits" .)