Lids slipped out of position (4)
I believe the answer is:
slid
'slipped out of position' is the definition.
'slid' can be an answer for 'slipped' ('slide' can be a synonym of 'slip'). I am unsure of the 'out of position' bit.
'lids' is the wordplay.
'lids' can be anagrammed to 'SLID'.
However, I am not sure how this is indicated.
Can you help me to learn more?
(Other definitions for slid that I've seen before include "Skidded, slewed" , "Moved smoothly along a surface" , "Moved (eg, on ice)" , "Slipped" .)