Signal Corps invading eastern country before Lawrence (8)
I believe the answer is:
indicate
'signal' is the definition.
(synonyms)
'corps invading eastern country before lawrence' is the wordplay.
'corps' becomes 'c' (military abbreviation for corps).
'invading' indicates putting letters inside.
'eastern country' becomes 'india' (I've seen this before).
'before' says to put letters next to each other.
'lawrence' becomes 'te' (TE Lawrence, Lawrence of Arabia).
'c' placed into 'india' is 'indica'.
'indica'+'te'='INDICATE'
(Other definitions for indicate that I've seen before include "Point out, make known" , "Mark" , "(Give a) signal" , "Point out, suggest" , "Point out or give some notion of" .)