The shape of football pitch in playing field introducing confusion (9)
I believe the answer is:
rectangle
'the shape of football pitch' is the definition.
(I've seen this before)
'playing field introducing confusion' is the wordplay.
'playing field' becomes 'rec' (short for recreation ground).
'introducing' is a charade indicator (letters next to each other) (some letters go before others).
'confusion' becomes 'tangle' (tangle is a kind of confusion).
'rec'+'tangle'='RECTANGLE'
'in' is the link.
(Other definitions for rectangle that I've seen before include "regular sort of figure" , "box" , "Geometric figure with four right angles, not square" , "Four sides involved in this" , "Parallelogram with four right angles" .)