Macros that clash with official man(7) macros must be defined
after .TH, or they fail to override the official ones because .TH
typically reloads the official macro file.

There is no proper fix: you shouldn't go and define private macros
in the first place.  Upstream could rename the macro (risking a clash
with something else, or risking portability to very old formatters if
going beyond a two-character macro name).  This is just a workaound.

Index: doc/tkTable.n
--- doc/tkTable.n.orig
+++ doc/tkTable.n
@@ -208,17 +208,6 @@
 .LP
 See the \\fBoptions\\fR manual entry for details on the standard options.
 ..
-'\"	# OP - start of full description for a single option
-.de OP
-.LP
-.nf
-.ta 4c
-Command-Line Name:	\\fB\\$1\\fR
-Database Name:	\\fB\\$2\\fR
-Database Class:	\\fB\\$3\\fR
-.fi
-.IP
-..
 '\"	# CS - begin code excerpt
 .de CS
 .RS
@@ -234,6 +223,17 @@ Database Class:	\\fB\\$3\\fR
 \\$1\l'|0\(ul'\\$2
 ..
 .TH table n 2.8 Tk "Tk Table Extension"
+'\"	# OP - start of full description for a single option
+.de OP
+.LP
+.nf
+.ta 4c
+Command-Line Name:	\\fB\\$1\\fR
+Database Name:	\\fB\\$2\\fR
+Database Class:	\\fB\\$3\\fR
+.fi
+.IP
+..
 .HS table tk
 .BS
 .SH NAME