Half a minute at present for fish (6)
I believe the answer is:
minnow
'fish' is the definition.
(minnow is a kind of fish)
'half a minute at present' is the wordplay.
'half a' means to take half the letters.
'at present' becomes 'now' (synonyms).
'minute' halved is 'min'.
'min'+'now'='MINNOW'
'for' acts as a link.
(Other definitions for minnow that I've seen before include "he's unimportant" , "A fish; insignificant person" , "Small fry" , "Very small freshwater fish of the carp family" , "unimportant person" .)