Agreement from Charlie about short trousers (7)
I believe the answer is:
concord
'agreement' is the definition.
(I know that agreement can be written as concord)
'charlie about short trousers' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'about' becomes 'on' (as in a book 'on' a certain topic).
'short trousers' becomes 'cord' (short for corduroy trousers; 'short' suggests a short form).
'c'+'on'+'cord'='CONCORD'
'from' is the link.
(Other definitions for concord that I've seen before include "Harmonious state of things" , "Amity" , "Agreement, harmony" , "Harmony; treaty" .)