Contributor to great pictures in big show certainly satisfied the Queen (8,5)
I believe the answer is:
exposure meter
'contributor to great pictures' is the definition.
(light meter in photography)
'big show certainly satisfied the queen' is the wordplay.
'big show' becomes 'expo' (I've seen this in another clue).
'certainly' becomes 'sure' (synonyms).
'satisfied' becomes 'met' (as in 'met the conditions of his contract').
'the queen' becomes 'ER' (Elizabeth Regina ie Queen Elizabeth).
'expo'+'sure'+'met'+'er'='EXPOSURE METER'
'in' is the link.
(Other definitions for exposure meter that I've seen before include "Film user's guide" , "Photographic instrument, now usually incorporated in camera" , "Photographic equipment" .)