Form lent grace, somehow (9)
I believe the answer is:
rectangle
'form' is the definition.
(rectangle is a kind of form)
'lent grace somehow' is the wordplay.
'somehow' indicates an anagram.
'lent'+'grace'='lentgrace'
'lentgrace' anagrammed gives 'RECTANGLE'.
(Other definitions for rectangle that I've seen before include "Geometric figure with four right angles, not square" , "Quadrilateral" , "Shape of football pitch" , "Parallelogram with four right angles" , "Figure on plane" .)