Judge almost doubtful for a moment (4)
I believe the answer is:
jiff
'moment' is the definition.
(thesaurus)
'judge almost doubtful' is the wordplay.
'judge' becomes 'j' (abbreviation for judge).
'almost' means to remove the last letter (most of the word but not all of it).
'doubtful' becomes 'iffy' (I've seen this before).
'iffy' with its last letter taken off is 'iff'.
'j'+'iff'='JIFF'
'for a' is the link.
(Other definitions for jiff that I've seen before include "Second" , "A mo" , "Two shakes" , "Instant (sl)" .)