Shady criminal with uncertainty over time period in work (3,5)

'period in work' is the definition.
'day shift' can be an answer for 'period' (day shift is a kind of period). I am unsure of the 'in work' bit.

'shady criminal with uncertainty over time' is the wordplay.
'criminal' indicates an anagram.
'with' says to put letters next to each other.
'uncertainty' becomes 'if' (if can mean a condition or uncertainty).
'over' is a charade indicator (letters next to each other) (in a down clue, some letters go over others).
'time' becomes 't' (abbreviation).
'shady' anagrammed gives 'daysh'.
'daysh'+'if'+'t'='DAY-SHIFT'

Can you help me to learn more?