Simply lock for solid support (8)
I believe the answer is:
buttress
'solid support' is the definition.
'buttress' can be an answer for 'support' (buttress is a kind of support). I'm not certain of the 'solid' bit.
'simply lock' is the wordplay.
'simply' becomes 'but' (I've seen this in other clues).
'lock' becomes 'tress' (both can mean a piece of hair).
'but'+'tress'='BUTTRESS'
'for' is the link.
Can you help me to learn more?
(Other definitions for buttress that I've seen before include "Supporting structure" , "Stanchion" , "strengthening side" , "Support built against a wall, prop" , "support for Notre Dame?" .)