Challenged about blocking father (5)
I believe the answer is:
dared
'challenged' is the definition.
(daring is a kind of challenging)
'about blocking father' is the wordplay.
'about' becomes 're' (common abbreviation for 'with reference to').
'blocking' is an insertion indicator.
'father' becomes 'dad' (dad is a kind of father).
're' placed within 'dad' is 'DARED'.
(Other definitions for dared that I've seen before include "was bold enough" , "Goaded" , "Challenged (to a deed)" , "Defied, challenged" , "Made bold" .)