Piece of text provided by soldier with diagram (9)
I believe the answer is:
paragraph
'piece of text' is the definition.
(several sentences)
'soldier with diagram' is the wordplay.
'soldier' becomes 'para' (para is a kind of soldier).
'with' says to put letters next to each other.
'diagram' becomes 'graph' (graphing is a kind of diagraming).
'para'+'graph'='PARAGRAPH'
'provided by' is the link.
(Other definitions for paragraph that I've seen before include "Section of writing" , "It's indicated with a new line and indentation, perhaps" , "Chunk of text" , "Subdivision of text" , "Section of written work" .)