Pitmen perhaps manoeuvring horse and cart (9)
I believe the answer is:
orchestra
'pitmen perhaps' is the definition.
(an orchestra is located in the pit in a theatre)
'manoeuvring horse and cart' is the wordplay.
'manoeuvring' is an anagram indicator.
'and' means one lot of letters go next to another (I've seen this in other clues).
'horse' after 'cart' is 'carthorse'.
'carthorse' with letters rearranged gives 'ORCHESTRA'.
(Other definitions for orchestra that I've seen before include "alternative to the organ" , "Large band of musicians" , "Other cars (anag.)" , "kitchen setting?" , "An assembly of musicians with various instruments" .)