Attempt to secure one pound for hat (6)
I believe the answer is:
trilby
'hat' is the definition.
(trilby is a kind of hat)
'attempt to secure one pound' is the wordplay.
'attempt' becomes 'try' (synonyms).
'to secure' is an insertion indicator (inserted letters are secured inside).
'one' becomes 'I' (Roman numeral).
'pound' becomes 'lb' (synonyms).
'i'+'lb'='ilb'
'try' going around 'ilb' is 'TRILBY'.
'for' is the link.
(Other definitions for trilby that I've seen before include "Indented felt hat" , "Hat named after fictional character" , "one by du Maurier?" , "A man's hat or novel by du Maurier" , "Miss O'Ferrall" .)