Employee having sex with young lady is unreliable (3,3,4)
I believe the answer is:
hit and miss
'unreliable' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'employee having sex with young lady' is the wordplay.
'employee' becomes 'hand' (hand is a kind of employee).
'having' indicates putting letters inside.
'sex' becomes 'it' (a common euphemism).
'with' means one lot of letters go next to another.
'young lady' becomes 'miss' (synonyms).
'hand' enclosing 'it' is 'hitand'.
'hitand'+'miss'='HIT-AND-MISS'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for hit and miss that I've seen before include "with no guarantee of success" , "Mixed" , "with no pattern" , "Random" , "verdicts jury once put on record" .)