Slippery customer takes months to track and select for jury duty (7)
I believe the answer is:
empanel
'select for jury duty' is the definition.
'slippery customer takes months to track' is the wordplay.
'slippery customer' becomes 'eel'.
'takes' is an insertion indicator.
'months' becomes 'm'.
'to track' becomes 'pan' (both can mean to slowly move, as in camera shots).
'm'+'pan'='mpan'
'eel' going around 'mpan' is 'EMPANEL'.
'and' acts as a link.
(Other definitions for empanel that I've seen before include "select jurors" , "Form jury" , "Make a juror" , "Men leap (anag.)" , "Select for jury service" .)