Hires for a song, to get involved in crime (5,2)
I believe the answer is:
signs on
'hires' is the definition.
(signing on is a kind of hiring)
'a song to get involved in crime' is the wordplay.
'to get involved' is an anagram indicator.
'in' indicates putting letters inside.
'crime' becomes 'sin'.
'song' is an anagram of 'gnso'.
'gnso' inserted inside 'sin' is 'SIGNS ON'.
'for' acts as a link.
(Other definitions for signs on that I've seen before include "Employs" , "Hires" .)