The Forces clergyman had been lying (8)
I believe the answer is:
chaplain
'the forces clergyman' is the definition.
'chaplain' can be an answer for 'clergyman' (chaplain is a kind of clergyman). I am not certain of the 'the forces' bit.
'been lying' is the wordplay.
I cannot quite see how this works, but
'been' could be 'lain' (lying is a kind of being) and 'lain' is found in the answer.
The remaining letters 'chap' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'had' acts as a link.
Can you help me to learn more?
(Other definitions for chaplain that I've seen before include "Member of the clergy, in 24 ac say" , "Army padre" , "Member of clergy ministering to an organisation" , "'Member of the clergy, in a hospital, say (8)'" , "Forces' clergyman" .)