Pieces of sculpture mostly standing on a pair of parallel lines (8)
I believe the answer is:
statuary
'pieces of sculpture' is the definition.
(multiple statues)
'mostly standing on a pair of parallel lines' is the wordplay.
'mostly standing' becomes 'statua' (I am not sure about this - if you are sure you should believe this answer much more).
'on' is a charade indicator (letters next to each other).
'a pair of parallel lines' becomes 'ry' (ry can be short for railway).
'statua'+'ry'='STATUARY'
Can you help me to learn more?
(Other definitions for statuary that I've seen before include "Carved or sculpted figures" , "Collection of carved or moulded figures" , "Collective sculptures" , "Range of sculpture" , "Carved figures collectively" .)