Ministry, at present, of fish? (6)
I believe the answer is:
minnow
'fish?' is the definition.
(minnow is a kind of fish)
'ministry at present' is the wordplay.
'ministry' becomes 'm' (this might be a standard abbreviation which I don't know about).
'at' becomes 'in' (synonymous in some cases - eg at school, in school).
'present' becomes 'now' (both can mean the current period).
'm'+'in'+'now'='MINNOW'
'of' is the link.
Can you help me to learn more?
(Other definitions for minnow that I've seen before include "Tiddler" , "he's unimportant" , "Small person" , "A fish; insignificant person" , "Very small freshwater fish of the carp family" .)