Y-fronts less than penny? Worker gets small (10)
I believe the answer is:
underpants
'y-fronts' is the definition.
(Y-fronts are a type of underwear)
'less than penny? worker gets small' is the wordplay.
'less than' becomes 'under' (I've seen this before).
'penny?' becomes 'p' (short for pence).
'worker' becomes 'ant' (worker is a type of ant).
'gets' says to put letters next to each other.
'small' becomes 's' (abbreviation - e.g. clothes size).
'under'+'p'+'ant'+'s'='UNDERPANTS'
(Other definitions for underpants that I've seen before include "drawers" , "Intimate clothing" , "Close-fitting garment" , "cover and support" , "Shorts" .)